BACKGROUND: Recently, the fate of emerging micro-contaminants in environmentally relevant samples has attracted considerable attention. Semiconductor photocatalysis may offer an appealing methodology to treat such contaminants; in this respect, the degradation of synthetic estrogen 17α-ethynylestradiol (EE2) employing simulated solar radiation and ZnO as the photocatalyst was investigated.

RESULTS: A factorial design approach was adopted to evaluate the effect of estrogen concentration (100–500 µg L⁻¹), ZnO concentration (50-500 mg L⁻¹ in suspension), treatment time (2-10 min), photon flux (4.93 × 10⁻⁷–5.8 × 10⁻⁷ einstein L⁻¹ s⁻¹) and the water matrix (ultrapure water and treated wastewater) on EE2 removal. The first four variables had a statistically important, positive effect on degradation, while the water matrix introduced a negative effect presumably due to the competition between EE2 and the effluent organic and inorganic matter for hydroxyl radicals and other oxidizing species. Moreover, second-order interactions of estrogen concentration with time and the water matrix were also significant. EE2 degradation follows first-order kinetics with the respective rate constants in wastewater and water being 9.2 ± 0.7 × 10⁻² and 41 ± 8 × 10⁻² min⁻¹ at the maximum ZnO concentration and photon flux. On the other hand, the removal rate of effluent's overall estrogenicity (as assessed by the yeast estrogen screening bioassay) was an order of magnitude lower than that of EE2, implying the presence of persistent estrogenic compounds in the photocatalyzed effluent.

CONCLUSIONS: An effective treatment process is demonstrated which benefits from the use of renewable energy and a stable and highly active photocatalyst. Copyright © 2012 Society of Chemical Industry

BACKGROUND: The bioconversion of whey into ethanol by immobilized Kluyveromyces marxianus in packed-bed and fluidized bioreactors is described. Both batch and continuous cultures were analyzed using three different strains of K. marxianus and the effect of the operating mode, temperature, and dilution rates (D) were investigated.

RESULTS: All immobilized strains of K. marxianus (CBS 6556, CCT 4086, and CCT 2653) produced similar high yields of ethanol (0.44 ± 0.01 g EtOH g⁻¹ sugar). Significant variations of conversion efficiencies (66.1 to 83.3%) and ethanol productivities (0.78 to 0.96 g L⁻¹ h⁻¹) were observed in the experiments with strain K. marxianus CBS 6556 at different temperatures. High yields of ethanol were obtained in fluidized and packed-bed bioreactors continuous cultures at different D (0.1 to 0.3 h⁻¹), with the highest productivity (3.5 g L⁻¹ h⁻¹) observed for D = 0.3 h⁻¹ in the fluidized bioreactor (87% of the maximal theoretical conversion), whereas the highest ethanol concentration in the streaming effluent (28 g L⁻¹) was obtained for D = 0.1 h⁻¹. Electronic micrographs of the gel beads showed efficient cell immobilization.

CONCLUSION: Batch and continuous cultivations of immobilized K. marxianus in fluidized and packed-bed bioreactors enable high yields and productivities of ethanol from whey. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Selenium removal from aqueous solutions can be a significant industrial problem, particularly in the metallurgical industry. In order to evaluate new reducing agents for this application, the reduction of selenious acid (H₂SeO₃) species with stannous ions (Sn²⁺) from weakly acidic sulfate solutions containing 300 mg L⁻¹ of selenium at 23 °C was studied.

RESULTS: At initial pH values < 1.3 and molar ratio ≥ 2, less than 0.5 µg L⁻¹ of selenium(IV) remained in solution after reduction. The reductive precipitation reaction started as soon as the stannous ions were added to the selenium-bearing solution and was completed in less than 5 min. The reaction products, characterized using X-ray diffraction, electron microscopy, particle and surface area measurements, X-ray photoelectron spectroscopy and chemical analysis, were composed of approximately equal amounts of tin selenide and tin dioxide. In addition to tin selenide a minor amount of selenium(IV) was found to be removed via adsorption on the tin dioxide formed in situ. Tests with a complex industrial solution also resulted in full and stable selenium precipitation.

CONCLUSION: Stannous ions were found to be very effective in removing selenious ions from synthetic and industrial solutions, producing very stable precipitates. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Tetrachloroethylene (PCE) and hexachloroethane (HCA) degradation, individually and in mixture, is investigated by Fe(III) or Fe(III)-citrate initiated Fenton reaction under a range of hydrogen peroxide (H₂O₂) concentrations to illustrate the applicability and constraints of Fenton chemistry in degrading contaminants in polluted groundwater.

RESULTS: In individual solutions Fe(III) rapidly degraded PCE for all H₂O₂ concentrations, but HCA at ≥ 0.2 mol L⁻¹ H₂O₂; the apparent PCE degradation rate initially increased but then decreased with increasing H₂O₂, while the HCA degradation rate was either unaffected or increased. With Fe(III)-citrate PCE degradation was lower and no HCA degradation occurred. PCE degradation was lower in PCE-HCA mixture, but the trend with H₂O₂ concentration was similar to the individual chemical; for HCA the residual was smaller for higher H₂O₂ concentration, but the apparent degradation rate constant was unaffected.

CONCLUSION: Fe(III) catalyzed reactions can potentially degrade chemicals through reductive as well as oxidative transformations. Degradation of chemicals in mixtures occurs at a slower rate due to competition for radical moieties. The Fe(III)-citrate complex further slowed chemical transformation. This study expands on the use of different forms of iron to catalyze the Fenton reaction to degrade chemicals. Copyright © 2012 Society of Chemical Industry

BACKGROUND: This research has assessed the impact of sulfate accumulation on the performance of two biofilters treating CS₂. Both biofilters were packed with a pelletized organic fertilizer and operated in downflow mode (Biofilter A) and flow reversal mode (Biofilter B). The performance of the biofilters after an excessive accumulation of sulfate has also been evaluated.

RESULTS: The excessive accumulation of sulfate and the reduction in the packing material's moisture content resulted in a decrease in the initial high removal efficiency recorded during the first 50 days (approx.) of operation in both biofilters. A recovery strategy based on mixing and washing the packing material led to a sustained RE of 40 ± 9% and 62 ± 11% for Biofilters A and B, respectively. Both biofilters recovered their initial performance after irrigation. A high CO₂:EC ratio suggested that secondary oxidation reactions related to heterotrophic bacteria occurred in both bioreactors. The maximum elimination capacity (EC_max) recorded in Biofilters A and B was 11.6 and 16.6 g CS₂ m⁻³ h⁻¹, respectively.

CONCLUSIONS: This study confirmed the capacity biofilters treating CS₂ have to recover after sulfate accumulation episodes and the importance of optimized irrigation strategies. The benefit of the flow reversal operating mode was highlighted. Copyright © 2012 Society of Chemical Industry

BACKGROUND; In this study, simultaneous photocatalytic degradation of four fluoroquinolone (FQ) compounds (i.e. ofloxacin, norfloxacin, ciprofloxacin and enrofloxacin) was investigated in TiO₂ suspensions under simulated solar light irradiation. Effects of experimental variables including pH, TiO₂ dosage, initial substrate concentration and hydrogen peroxide (H₂O₂) on the degradation processes were also investigated.

RESULTS: The antibiotics degradation was pH-influenced. The photocatalytic reaction followed the pseudo-first-order model, with reaction rate constants (k) 0.026, 0.027, 0.022 and 0.026 min⁻¹ for ofloxacin, norfloxacin, ciprofloxacin and enrofloxacin, respectively. Complete elimination of four FQs was achieved in a reaction system composed of 0.5 g L⁻¹ of TiO₂ and 82.5 mg L⁻¹ of H₂O₂ at pH 6 after 90 min irradiation. Mineralization of FQs during TiO₂ photocatalysis was slower than the FQs conversion, and the antibacterial activity of the four FQs was completely removed by TiO₂ under simulated solar light irradiation.

CONCLUSION: The four FQs can be simultaneously degraded and mineralized with commercially available TiO₂ under simulated solar light irradiation. Microbiological analysis showed that the antibacterial activity of the four FQs was completely removed. These results are helpful for antibiotics removal in the environment, and for exploring new technology for wastewater treatment. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Progesterone is considered an endocrine disruptor chemical. It can be found in industrial discharges, municipal wastewaters, and, in some instances, even in treated effluents at the level of ng dm⁻³.

RESULTS: Conductive diamond electrolysis can be used to remove progesterone from aqueous solutions. Increases in current density lead to less efficient processes, indicating mass transfer control of the process rate. Occurrence of chlorides in the electrolytic media favors the depletion of progesterone compared with sulphates, although it does not affect the mineralization rate. Independently of the solubilizing agent used, the process behaves similarly during a first stage of the electrolysis (at the four ranges of pollutant concentration studied). However, in a second stage, the rate changes abruptly due to reduced action of hydroxyl radicals in methanol media.

CONCLUSIONS: Progesterone can be removed efficiently by conductive diamond electrolysis from aqueous solutions within the range of initial concentrations 10⁻² to 10² mg dm⁻³. The process efficiency increases with the current density. Removal rate does not depend on the nature of the electrolyte, but this parameter affects the intermediates formed during the experiment. When pure methanol is used as solubilizing agent, only direct electro-oxidation takes place. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Membrane fouling in downstream processing has become a major obstacle in enzyme production. The use of a membrane with high surface hydrophilicity may be an acceptable way to overcome this problem. In this study, the effects of dip time on chitosan incorporation were investigated to produce a low fouling ultrafiltration membrane for trypsin separation.

RESULT: Pristine ultrafiltration membrane with a polymer concentration of 15% was developed via phase inversion. Membrane surface modification was performed using chitosan solution with different dip times. Membranes with a 60-min dip time provided optimum trypsin transmission (about 91.8%). Such membranes have a high permeability coefficient (71 L m⁻² h⁻¹) and good porosity (about 89.6%). The hydrophilicity of this modified membrane was also improved by 50% compared with the native membrane, and its flux recovery was about 89.8%. The successful assembly of chitosan onto the membrane's surface was ascertained by ATR-FTIR and X-ray diffractometry (XRD). The morphology of this membrane was significantly different from that of native membrane.

CONCLUSION: The experimental results show that membrane dip time exerts a significant influence on the self-assembly of chitosan particles onto the membrane's surface, and this process can be used to produce a potentially low-fouling UF membrane for trypsin separation. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Alkaline sulfite/anthraquinone (ASA) cooking of Pinus radiata and Pinus caribaea wood chips followed by disk refining was used as a pretreatment for the production of low lignified and high fibrillated pulps. The pulps produced with different delignification degrees and refined at different energy inputs (250, 750 and 1600 Wh) were saccharified with cellulases and fermented to ethanol with Saccharomyces cerevisiae using separated hydrolysis and fermentation (SHF) or semi-simultaneous saccharification and fermentation (SSSF) processes.

RESULTS: Delignification of ASA pulps was between 25% and 50%, with low glucans losses. Pulp yield was from 70 to 78% for pulps of P. radiata and 60% for the pulp of P. caribaea. Pulps obtained after refining were evaluated in assays of enzymatic hydrolysis. Glucans-to-glucose conversion varied from 20 to 70%, depending on the degree of delignification and fibrillation of the pulps. The best ASA pulp of P. radiata was used in SHF and SSSF experiments of ethanol production. Such experiments produced maximum ethanol concentration of 20 g L⁻¹, which represented roughly 90% of glucose conversion and an estimated amount of 260 L ethanol ton⁻¹ wood. P. caribaea pulp also presented good performance in the enzymatic hydrolysis and fermentation but, due to the low amount of cellulose present, only 140 L ethanol would be obtained from each ton of wood.

CONCLUSION: ASA cooking followed by disk refining was shown to be an efficient pretreatment process, which generated a low lignified and high-fibrillated substrate that allowed the production of ethanol from the softwoods with high conversion yields. Copyright © 2012 Society of Chemical Industry

BACKGROUND: A study of the removal of arsenic from a sample of actual groundwater using crosslinked xanthated chitosan is described.

RESULTS: Removal of As(III) and As(V) was studied at pH 7.5 under equilibrium and dynamic conditions. The equilibrium data were fitted to Langmuir and Freundlich adsorption models and the various model parameters evaluated. The monolayer adsorption capacity from the Langmuir model for xanthated chitosan flakes (XCF) (As(V) 20.0 ± 0.56 mg g⁻¹; As(III) 33.0 ± 0.32 mg g⁻¹) were lower than obtained for xanthated chitosan granules (XCB) (As(V) 36.0 ± 0.52 mg g⁻¹; As(III) 48.0 ± 0.45 mg g⁻¹). Adsorption of As (V) was unaffected by the presence of other anions while in the case of As(III) the presence of sulfate and silicate caused a 26.5–50.9% decrease in adsorption. A sample (940 bed volumes) of a groundwater spiked with 200 µg L⁻¹ As(V) treated with XCF in column experiments reduced the arsenic concentration to < 10 µg L⁻¹. The adsorbent was also successfully applied for the removal of total inorganic arsenic down to < 10 µg L⁻¹ from real samples of arsenic-contaminated groundwater.

CONCLUSION: Xanthated chitosan was an efficient adsorbent for the removal of both forms of arsenic from groundwater under near neutral conditions. The presence of sulfur and the amino groups resulted in increased adsorption capacity of the sorbent. Copyright © 2012 Society of Chemical Industry

BACKGROUND: The removal of styrene from air streams in a co-current gas-liquid downflow trickle-bed bioreactor (TBB) inoculated with Pseudomonas sp. E-93486 strain was studied experimentally. The experiments were conducted to determine such parameters of the bioprocess as gas and liquid flow rates and specific styrene loading for which maximum elimination capacity was achieved.

RESULT: The effect of inlet styrene concentration in gas phase on its degradation was studied in the range from 0.08 to 1.1 g m⁻³. The recirculation rate of the liquid medium was changed from 0.17 to 0.35 m³ h⁻¹ whereas the gas flow rate was changed in the range from 1.2 to 6 m³ h⁻¹. The treatment of air streams contaminated with styrene in a trickle-bed bioreactor was described with a mathematical model. The model incorporates mass transfer in both the gas and liquid phases and a biological reaction in biofilm. The rate of the partial stages of the process was determined experimentally. Microbial growth tests in the presence of styrene as the sole carbon and energy source were performed both in batch and continuous cultures. The Haldane model was used to describe Pseudomonas sp. E-93486 strain growth kinetics on styrene.

CONCLUSION: The experiments conducted showed high activity of the examined bacterial strain in the styrene biodegradation process and relatively low sensitivity to inhibition of its growth at higher concentrations of styrene in the solution. The results of the experiments carried out in TBB were compared with the values obtained from a mathematical model. Satisfactory compatibility of the calculated and experimental data was obtained. Copyright © 2012 Society of Chemical Industry

BACKGROUND: The purpose of this study was to investigate the co-treatment of olive-mill wastewater (OMW) and municipal wastewater in activated sludge systems operating in the absence and presence of different adsorbent materials and to study the role of sorption and biodegradation in total phenols removal.

RESULTS: Batch experiments were initially conducted to investigate total phenols' adsorption capacity on activated sludge (AS), olive pomace (OP) and powdered activated carbon (PAC). According to the results, PAC presented the best adsorption capacity. Three sequencing batch reactors (SBRs) were also operated, treating municipal wastewater and different amounts of OMW. The first SBR contained AS (AS-System), the second AS and OP (AS-OP System) and the third AS and PAC (AS-PAC System). All SBRs operated sufficiently in the presence of 1% v/v OMW, achieving mean COD and total phenols removal efficiency higher than 86% and 85%, respectively, and satisfactory settling capacity. Increase of OMW concentration to 5% v/v affected the performance of SBRs, resulting in mean COD removal efficiencies that ranged between 61% (AS-OP System) and 80% (AS-PAC System).

CONCLUSION: Among the SBRs used, the AS-PAC System operated with highest performance in the presence of 1 and 2.5% v/v OMW, and showed better stability in the presence of 5% v/v OMW. Calculation of total phenols mass flux revealed that biodegradation was the principal mechanism of their removal. The highest values of mean biotransformation rates were calculated for the AS-PAC System and ranged between 2.0 and 40.6 d⁻¹ for different experimental phases. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Poly(3-hydroxybutyrate-co-3-hydroxyvalerate) [P(3HB-co-3HV)] co-polymer has immense potential in the field of environmental and biomedical sciences as biodegradable and biocompatible material. The present study examines a filamentous N₂-fixing cyanobacterium, Nostoc muscorum Agardh as a potent feedstock for P(3HB-co-3HV) co-polymer production and characterization of co-polymer film for commercial applications.

RESULTS: Under photoautotrophic growth conditions, N. muscorum Agardh accumulated the homopolymer of poly-β-hydroxybutyrate (PHB), whereas synthesis of P(3HB-co-3HV) co-polymer was detected under propionate- and valerate-supplemented conditions. Exogenous carbons such as acetate, fructose and glucose supplementation with propionate/valerate was found highly stimulatory for the co-polymer accumulation; the content reached 58–60% of dry cell weight (dcw) under P-/N-deficiencies with 0.4% acetate + 0.4% valerate supplementation, the highest value reported so far for P(3HB-co-3HV) co-polymer-producing cyanobacterial species. The material properties of the films were studied by mechanical tests, surface analysis and differential scanning calorimetry (DSC).

CONCLUSION:N. muscorum Agardh, a photoautotrophic N₂-fixing cyanobacterium, emerged as a potent host for production of P(3HB-co-3HV) co-polymer with polymer content 60% of dry cell weight. The material properties of the films were found to be comparable with that of the commercial polymer, thus advocating its potential applications in various fields. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Biodegradation of diesel hydrocarbons using bioreactors has been proposed as an alternative for diesel contaminated sites remediation. To make this alternative feasible, several factors must be optimized or improved: reducing hydraulic retention times (HRT) and applying design methods to enhance the access of the microorganisms to low soluble and recalcitrant compounds like hydrocarbon fuels. In the present work a time and cost efficient continuous-flow packed bed bioreactor at low HRT was designed and evaluated. The effect of non-previously studied anionic surfactant GAELE (glycolic acid ethoxylate lauryl ether) was also investigated.

RESULTS: A continuous-upflow packed bed bioreactor (CPR) was built using an inexpensive support made of volcanic and alluvial stones. The biodegradation experiments conducted with a 12-month-old biofilm at a fixed HRT of 0.5 h, recorded removal of up to 97.9% at a diesel concentration of 1120 mg L⁻¹ with GAELE. A first-order rate constant of 0.10 h⁻¹ was calculated. Kinetic analysis using Arvin's model, which introduces mass transfer to the biofilm, showed statistical differences in the kinetic rate parameters (P < 0.001). Moreover, GAELE significantly increased biodegradability at high concentrations, with BOD₅ and COD removals up to 90.8 and 80.7%, respectively. Putative hydrocarbon degrading bacteria responsible for the degradation under nitrate-reducing conditions were positively identified.

CONCLUSIONS: The continuous-upflow packed bed reactor was capable of high percentage diesel biodegradation at short HRTs. The use of GAELE increased diesel availability and thus enhanced hydrocarbon removal. Therefore, CPR packed with volcanic and alluvial stones combined with GAELE showed potential for the remediation of diesel-impacted sites. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Chitosan membranes were formed through a phase inversion technique and then cross-linked with epichlorohydrin (CHX). Heterogeneous graft copolymerization of itaconic acid (IA) onto membrane was carried out with different monomer concentrations (CHX-g-p(IA)). The membrane properties such as equilibrium swelling ratio, porosity, and contact angle were measured, together with analysis by scanning electron microscopy (SEM), energy dispersive analysis of X-rays (EDAX), atomic force microscopy (AFM), and Fourier transform infrared (FTIR) spectroscopy.

RESULTS: The Cu(II) ion incorporated membranes (i.e. CHX-g-p(IA)-Cu(II)) were used for reversible immobilization of laccase using CHX-g-p(IA) membrane as a control system. Maximum laccase adsorption capacities of the CHX-g-p(IA) and CHX-g-p(IA)-Cu(II) membranes (with 9.7% grafting yield) were found to be 6.3 and 17.6 mg mL⁻¹ membrane at pH 4.0 and 6.0, respectively. The K_m value for immobilized laccase on CHX-g-p(IA)-Cu(II) (4.16 × 10⁻² mmol L⁻¹) was 2.11-fold higher than that of free enzyme (1.97 × 10⁻² mmol L⁻¹). Finally, the immobilized laccase was used in a batch system for degradation of three different dyes (Reactive Black 5, RB5; Cibacron Blue F3GA, CB; and Methyl Orange, MO). The immobilized laccase on CHX-g-p(IA)-Cu(II) membrane was more effective for removal of MO dye than removal of CB and RB5 dyes.

CONCLUSION: Flexibility of the enzyme immobilized grafted polymer chains is expected to provide easy reaction conditions without diffusion limitation for substrate dye molecules and their products. The support described, prepared from green chemicals, can be used for the immobilization of industrially important enzymes. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Specific energy consumption (SEC) is an important factor in electrochemical treatment of wastewaters. SEC during electrochemical treatment of food industry wastewaters, specifically deproteinated whey wastewater (DWW), simulated sugar beet factory wastewater (SFW) and fruit juice factory wastewater (FJW), were investigated in this study. The effects of operational parameters applied voltage, and electrolyte and wastewater concentrations on SEC were assessed and optimized.

RESULTS: SEC values were found in the range of 0.27–148.65, 0.94–375.76 and 0.20–636.40 kWh (kg COD)⁻¹ for DWW, SFW and FJW, respectively, after 8 h of reaction. Operational parameters were optimized at 25 °C through response surface methodology (RSM) where applied voltage was kept in the range (2–12 V), wastewater concentration and COD removal percent were maximized electrolyte concentration and SEC were minimized. Optimum conditions were estimated as 7.73 V applied voltage and 100% wastewater concentration in the presence of 27.11 g L⁻¹ supporting electrolyte concentration to achieve 25.02, 67.74 and 43.10% COD removal for DWW, SFW and FJW with corresponding SEC values of 17.85, 22.79 and 80.47 kWh (kg COD)⁻¹, respectively.

CONCLUSIONS: Providing further research on the reduction of SEC values, application of electrochemical treatment to food industry wastewaters with non-biodegradable components may become an alternative to conventional methods. Copyright © 2012 Society of Chemical Industry

BACKGROUND: The dissolution of wood and the regeneration of compounds such as cellulose and lignin is one of the challenges currently facing biorefineries. Lignin can be processed and employed for value-added products; therefore, environmentally friendly methods for wood solubilization and lignin regeneration are required and ionic liquids (ILs) offer an attractive alternative approach.

RESULTS: Dissolution of Pinus radiata and Eucalyptus globulus woods in imidazolium-based ILs (1-butyl-3-methylimidazolium acetate, 1-ethyl-3-methylimidazolium acetate and 1-ethyl-3-methylimidazolium chloride) was studied as well as the regeneration of lignin from wood liquors. The dissolution of wood in ILs was verified using an optical microscope to select the most appropriate ILs and the best experimental time and temperature conditions. Lignin was regenerated from wood dissolved in 1-ethyl-3-methylimidazolium chloride after 24 h at 150 °C by precipitation with an antisolvent. The regenerated solid was analyzed by Fourier transform infrared spectroscopy and compared with Indulin AT (reference). Furthermore, the influence of the wood dissolution time, the antisolvent employed and the antisolvent/wood solution ratio in the lignin recovery was studied.

CONCLUSIONS: The current study shows that 1-ethyl-3-methylimidazolium chloride can be employed effectively to dissolve wood at 150 °C for 24 h and lignin can be regenerated using methanol or ethanol as antisolvents. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Evaluation of the biodegradation interactions between styrene and acetone, two typical paint solvents and vapor phase pollutants differing in water solubility and biodegradability, was conducted both in a trickle bed reactor (TBR) and a biofilter (BF). The loading rate experiments were performed by increasing the acetone concentration in the inlet air while keeping the styrene concentration and loading rate constant.

RESULTS: At acetone loading rates (OL_AC) between 25 and 35 g_c m⁻³ h⁻¹, the BF featured greater steady state performance characteristics for styrene degradation. At OL_AC between 35 and 48 g_c m⁻³ h⁻¹, a decline of removal efficiency (RE) was observed for both pollutants, due to the system's overloading with acetone. Increasing OL_AC above 52-55 g_c m⁻³ h⁻¹ in both reactors resulted in drifts of RE and EC over time to much lower values. A step-drop of acetone loading rate back to OL_AC of 3 g_c m⁻³ h⁻¹ (g_c denotes grams of carbon) resulted in lag periods lasting for several hours.

CONCLUSIONS: Two important issues inherent for acetone biofiltration, e.g., from paint booths or polystyrene production, were identified: (1) poor performance at high loadings of this aggressive solvent and (2) acetone back-stripping into the air following periods of high overloading. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Dissolved oxygen is a key parameter in the biological removal of gaseous H₂S since sulfide-oxidizing bacteria convert H₂S into elemental sulfur instead of sulfate under limiting dissolved oxygen concentrations. Elemental sulfur is insoluble in water and accumulates in the packing material in biotrickling filters, increasing the pressure drop and operating costs. A set of mass transfer tests was performed in a versatile pilot plant to supply the necessary oxygen for the biological oxidation of H₂S. The plant can be operated with three different commercial gas–liquid contactor devices: a venturi ejector, a jet-venturi and a diffuser. The effects of different geometric and operating parameters have been tested for each device (including pressure rise and sulfate content to mimic real wastewater treatment plant conditions).

RESULTS: Results showed that the bioreactor pressure has a strong influence on the mass transfer characteristics of the three oxygenation devices. In addition, the ionic strength of the solution has a low influence on the mass transfer process.

The SOTE values obtained for the diffuser, jet-venturi and venturi ejector were 8.7%, 7.2% and 6.0%, respectively (pure water experiments), while SAE values were in the range 6.3–5.5 × 10⁻², 4.1–4.8 × 10⁻¹ and 3.1–3.7 × 10⁻¹ kg O₂ kW⁻¹ h⁻¹, respectively.

CONCLUSIONS: The jet-venturi offers the best oxygen transfer with lower power consumption compared with the diffuser and venturi ejector. The practical implementation of the most efficient aeration technology is possible from both technical and economical perspectives. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Underground car parks are confined spaces where traffic generates many pollutants such as toluene, ethylbenzene and xylene (TEX) and nitrogen oxides (NOx). The objective of this work was to evaluate the removal efficiency of low concentrations of TEX using planted and non-planted biofilters. Two pilot-scale units of biofiltration were set up. The gaseous mixture was generated to obtain a total TEX concentration of 600 µg m⁻³. Elimination performance of both biofilters was monitored for 96 days. Microbial behavior and the potential capacity to degrade the NOx, were investigated.

RESULTS: The removal efficiency (RE) was 30% in the non-planted and 15% in the planted biofilter at day 3. The RE decreased more rapidly in planted biofilter than in non-planted until nutrient addition at day 77. Consequently, the RE increased to 70% in both reactors. The potential for carbon mineralization was higher than those found in soils. The denitrification activity indicated good conditions for synthesis and maintenance of the denitrifying enzyme pool in the mound of soil. This suggested that NOx could also be treated in such a system.

CONCLUSION: The efficiency of the planted biofilters in removing TEX was evaluated and found to have good potential for improving air quality. Copyright © 2012 Society of Chemical Industry

BACKGROUND: European Union environmental policy has focused on abatement of volatile organic compounds (VOCs) from industrial emissions, and new European VOC emission limits have been established. This study analyzes the performance of a composite membrane bioreactor treating air stream contaminated with ethyl acetate, n-hexane and toluene under continuous and intermittent feeding conditions.

RESULTS: The system was operated under continuous feeding conditions: removal efficiencies (REs) higher than 99% were obtained for inlet loads up to 200 g m⁻³ h⁻¹ and empty bed residence times (EBRTs) as short as 15 s for ethyl acetate. A maximum elimination capacity of 75 g m⁻³ h⁻¹ (RE ∼66%) at an EBRT of 60 s was obtained for toluene. The system was unable to degrade n-hexane when a 1:1:1 ethyl acetate:n-hexane:toluene was supplied. Intermittent feeding with pollutants supplied for 16 h day⁻¹, 5 days week⁻¹, did not significantly affect the system performance. CO₂ production recovered within 1-2 h and 12 h after night and a weekend closures, respectively.

CONCLUSIONS: The membrane bioreactor has been shown to be effective for controlling air emissions and this study illustrated the capacity of the system to handle intermittent feeding conditions that are common in industrial practices. Copyright © 2012 Society of Chemical Industry

Magnetic nanoparticles (5–100 nm in diameter) offer the science community a new dimension in many key areas of research, notably nano-medicine. However, use as catalyst support material (including enzyme immobilization) has largely been overlooked despite the benefits of a facile catalyst separation post-reaction with reuse through the application of an external magnetic field. This is largely due to the high cost associated with magnetic nanoparticle synthesis in addition to enzyme operating costs. This can, however, be compensated for by effective catalyst recycling in the production of high value chemicals, particularly chiral drugs and their intermediates, circumventing laborious multi-stage separation and purification procedures in conventional synthesis. Indeed, enzymes (such as lipase) on magnetic carriers have shown prolonged activity in organic solvents, even after recycling, when compared with free enzymes. Further developments can be directed at multi-functional magnetic nanoparticles with the creation of a reactant-specific micro-environment to facilitate multi-stepped reactions. The potential of enzyme-magnetic nanoparticle hybrids is discussed and applications in the synthesis of fine chemicals, including precursors for drugs, are identified. Copyright © 2012 Society of Chemical Industry

BACKGROUND: This study deals with the potential of biological processes combining biofiltration and a biotrickling filter to treat a mixture of sulphur reduced compounds (SRC) including dimethylsulfide (DMS), dimethyldisulfide (DMDS) and hydrogen sulphide (H₂S). The first step in this work is to evaluate the influence of pH on SRC biodegradation in microcosms seeded with planktonic biomass from activated sludge of a rendering facility. In a second step, for each tested pH, evaluation of the influence of pH on total bacterial community diversity and structure has been investigated using denaturing gradient gel electrophoresis (DGGE).

RESULTS: At pH 7 and 5, H₂S, DMS and DMDS were completely removed. In return, the abatement of DMS and DMDS is low, around 20%, for pH 3 and pH 1 microcosms. The selective pressure imposed in the microcosms (concentration and pH) is sufficient to influence strongly the community diversity and composition. The inoculum community seems to make a significant contribution to the 67-day community in the considered pH microcosms.

CONCLUSION: These results suggest that distinct communities from different inocula can achieve high and stable functionality. The results obtained provide relevant information for improving the treatment of different SRC using biotrickling filter/biofilter combination. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Shear enhanced membrane modules are becoming popular as they enable high permeate flux in almost all membrane filtration processes due to the high shear rate they generate at the membrane surface. In this article, the design of a new shear enhanced module with unique hydrodynamic cleaning facility is proposed. The device, presently at laboratory scale was named the Spinning Basket Membrane (SBM) module because of its inherent structural similarity with the well known Spinning Basket Reactor. An aqueous solution of polyethylene glycol was chosen as test fluid for the present study.

RESULTS: The module was characterized under different parametric conditions of transmembrane pressure (TMP), feed concentration (C₀) and rotational speed of the basket (Ω). It was observed that with its inbuilt cleaning facility the module was able to restrict the flux decline to within 15% of its start up value, even after 21 h of continuous running, with a maximum initial flux as high as 612 L m⁻² h⁻¹.

CONCLUSION: Based on the performance of the module, it may be concluded that this module could be scaled up for nearly uninterrupted industrial operation with reduced requirement for chemical cleaning, which is rare in the membrane industry to date. Copyright © 2012 Society of Chemical Industry

BACKGROUND: A new design for a methanol plant is proposed in which CO₂ addition, as one of the important parameters, is used to optimize the synthesis gas composition. An attempt has been made to assess the environmental features as well as the process operability of the proposed plant, in which the required CO₂ is provided from reformer flue gas. As a starting point, simulation of a conventional reference methanol case (RMC) and also the proposed green integrated methanol case (GIMC) are performed to obtain operational and kinetic parameters. In order to compare properly GIMC and RMC, the objective function is defined so that SynGas production, and thereby methanol production, in the GIMC is equal to that of the RMC.

RESULTS: In the optimization the optimum values of decision variables are calculated using a genetic algorithm. In the best case, the eco-efficiency indicators of GIMC would decrease to 330.3 kg CO₂ tonne⁻¹ MeOH, which is 15% lower than that of RMC. The environmental damage cost of 2.9 million dollars could also be prevented in GIMC when compared with RMC.

CONCLUSION: It was found that the CO₂ needed in GIMC could be provided by an environmentally friendly process and that the GIMC is a cleaner process compared with RMC. Furthermore, the proposed GIMC would be capable of reducing CO₂ emission while its mitigation potential depends significantly on the type of solvent employed in the GIMC. The results obtained show that environmental damage cost would be important and should be considered in the process design. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Downstream processing plays a crucial role in biotechnological production processes. Product concentration and purification require complex, multi-step operations, using significant amounts of chemical and auxiliary material. Today, design and optimization is important because the process development of biotechnological products is becoming more and more expensive. It is of great importance to improve sustainable development of eco-efficient products and processes. Integrated process and product development leads to more efficient use of raw materials.

RESULTS: A new stepwise approach is proposed to develop recycling strategies for biopharmaceutical products, which can be implemented within an existing and approved process environment. This article describes the approach in detail and exemplifies the methodical procedure for characteristic reference processes. The theoretical recycling and separation tasks as well as possible strategies are defined and evaluated experimentally. An experimental model parameter determination in small scale is shown. In addition, concrete solutions are discussed due to solving regulatory constraints addressing comparability studies.

CONCLUSION: It is shown that development with the aim of intensification and full integration of the individual steps of bioprocess production (modules, unit operations) leads to an improvement in every single step at the same time. It follows clearly that consistent implementation represents a meaningful contribution to next generation bioproduction design. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Synthetic ligands have conventionally been used for the preparation of homogenous Rh complex catalyst but biomass has rarely been utilized for this purpose. In the present investigation, plant tannins (natural polyphenols) were used as water-soluble ligands for the preparation of homogenous Rh³⁺ complex catalysts.

RESULTS: Based on X-ray photoelectron spectroscopy (XPS) and proton nuclear magnetic resonance (HNMR) analyses, the preparation mechanism of these complex catalysts was proven to involve chelating interactions between Rh³⁺ and the adjacent phenolic hydroxyls of plant tannins. As a result, the use of plant tannin promoted aqueous-organic biphasic interactions and the plant tannin-chelated Rh³⁺ complex catalysts exhibited much higher catalytic activity than commercial Rh complex catalysts in the biphasic hydrogenation of quinoline. Furthermore, the plant tannin-chelated Rh³⁺ complex can be reused three times without significant loss of catalytic activity

CONCLUSION: Our experimental results suggested that black wattle tannin (BWT) can be used as water-soluble ligands for the preparation of highly active and recyclable Rh³⁺ complex catalysts. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Industrial waste-water is posing an ever-greater environmental hazard. Recently, a process for purification combining activated carbon adsorption and microwave regeneration has drawn much attention. In this study, the effectiveness of this process for the treatment of industrial waste-water from a chemical plant was tested.

RESULTS: The effects of various factors including solution pH, granular activated carbon (GAC) dosage and contact time on the adsorption efficiency of organic compounds were studied. The regeneration of the exhausted GAC under microwave radiation was investigated, and the optimal conditions were: microwave power 400 W, radiation time 3 min for 10 g GAC. Under the optimal conditions the regenerated GAC recovered 97.6% of its original adsorption capacity. Repetitive uses of the GAC showed that it maintained a stable performance in the first few repetitions, but a decrease was observed after further repetitions. A GAC weight loss of about 10% at the sixth repetition was observed and a decrease in the surface area and increase in the surface basicity were observed for the regenerated GAC. Economic evaluation of the microwave regeneration process suggested that the total cost was about 24.3% of the GAC price at a pilot scale.

CONCLUSIONS: A satisfactory regeneration of the chemical waste-water exhausted GAC could be achieved under microwave radiation. The GAC adsorption-microwave regeneration process was applicable for the treatment of this chemical waste-water. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Use of flocculation in wastewater treatment involves interactions of polymer with suspended solids and some dissolved organic compounds that can have a significant impact on aggregation process.

RESULTS: It was found that a strong interaction between cationic compounds and dissolved pigments in anaerobically digested (AD) wastewater occurred. The interactions were investigated by light adsorption of the pigments using a commercial flocculant added in the solutions and through a liquid–liquid extraction method using a model cationic surfactant (CTAB) dissolved in organic solvents. The absorbance of pigments decreased significantly with added cationic flocculant as the pigments and flocculants formed insoluble complexes that were removed by centrifugation.

CONCLUSION: The absorbance results indicate that the pigments can form complexes even at high concentrations (e.g. 2000 mg L⁻¹) of the flocculants. In addition, the extraction results demonstrated that pigments in the aqueous phase were transferred into the CTAB organic phase due to a strong interaction between the pigments and CTAB. These results suggest that the pigments present in AD effluent could be a negative factor for the flocculation process, probably resulting in the need for a high dosage of flocculants. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Enantioselective bioreduction of acetophenone to S-(−)-1-phenylethanol by Saccharomyces cerevisiae under non-growth conditions is inhibited by the product created. This study investigated the possibility of intensification and mathematical simulation of 1-phenylethanol production using periodic product removal carried out by membrane extraction in a hollow fiber membrane module.

RESULTS: The highest reaction rate was observed at the beginning of the biotransformation. With increased product concentration in the reaction medium, the reaction rate gradually decreased by about 50% after 20 h of biotransformation. The low concentration of product maintained in the reaction medium using membrane extraction had positive influence on the 1-phenylethanol production with a high yield (96%) and mean reaction rate of 0.226 mg h⁻¹g⁻¹, 35% higher than biotransformation without product removal. The equilibrium change and membrane fouling caused by biomass were not significant. It was possible to mathematically simulate the whole course of the extractive biotransformation with good agreement with experimental data.

CONCLUSION: Bioreductive production of 1-phenylethanol is more effective when using periodic membrane extraction of the product from the fermentation broth, which gives higher reaction rate, higher yield and simpler downstream process than biotransformation without product removal. Copyright © 2012 Society of Chemical Industry

BACKGROUND: The high crystallinity of cellulose underlies the recalcitrance that this polymer presents in enzymatic degradation. Thus, a pre-treatment step is applied in most bioconversion processes. Treatments with ionic liquids are considered an emerging pre-treatment technology, owing to their high efficiency in solvating cellulose, over molecular solvent systems.

RESULTS: Crystalline cellulose with and without ionic liquid (1-ethyl-3-methylimidazolium acetate) treatment, both commercially available, were used as substrates in enzymatic hydrolysis reactions using the earlier evaluated cellulolytic system of Fusarium oxysporum. The in situ removal of the hydrolysate during reactions enhanced the reaction rate as well as the overall glucose production. Ionic liquid treatment significantly decreased cellulose crystallinity and enhanced bioconversion yields and rates. The effects of cellulose structural changes during treatment on hydrolysis rate were investigated and the recalcitrance constants were determined.

CONCLUSION: The study showed that ionic liquid-treated cellulose became more homogeneous and more easily degradable than the untreated cellulose, a conclusion that was expressed mathematically by the difference in the recalcitrance constants for the two substrates. It was concluded that glucose production from ionic liquid-treated cellulose could achieve very high conversion yields in consolidated bioprocesses or during simultaneous saccharification and fermentation. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Chiral solvent extraction is a potentially attractive chiral separation technique. It is essential to know the intrinsic complexation kinetics for selection, design and operation of reactive extraction equipment and for reliable scale-up. The objective of this research is to study the kinetics of biphasic recognition chiral extraction of α-cyclohexyl-mandelic acid (α-CHMA) enantiomers using a modified Lewis cell.

RESULTS: The experimental results demonstrate that the extraction reaction kinetics is fast, and the reactions are first order with respect to α-CHMA and second order with respect to D-IBTA, with forward rate constants of 6.54 × 10⁻⁴ mol⁻² m⁶ s⁻¹ for S-α-CHMA and 6.84 × 10⁻⁴ mol⁻² m⁶ s⁻¹ for R-α-CHMA. With increase of HP-β-CD concentration in aqueous phase, enantioselectivity increases, while the overall mass transfer coefficients decrease.

CONCLUSIONS: Sufficient enantioselectivity and fast kinetics of extraction can be obtained in the BRCE system at HP-β-CD concentration of 0.1 mol L⁻¹ and D-IBTA concentration of 0.2 mol L⁻¹. These data will be useful in the design of extraction processes. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Bacterial hydrogen evolution releases excess electrons or energy formed during the metabolic oxidations. Until now, few studies have investigated the global regulation of cellular energy flows, pertaining to bacterial hydrogen production for the improvement of hydrogen production. In this study, the cellular energy metabolism of Enterobacter aerogenes was regulated by the addition of pyrophosphate (PPi) and the overexpression of polyphosphate kinase (PPK), to improve hydrogen production.

RESULTS: By overexpressing PPK at 10 mmol L⁻¹ PPi, total hydrogen yields were increased by 32.7%. Metabolic flux analysis demonstrated that overexpression of PPK in E. aerogenes resulted in a higher cellular ATP level and a higher NADH consumption rate, which changed the cellular redox state and allowed more electrons to flow into the hydrogen production pathway.

CONCLUSION: Alteration of the energy metabolism in E. aerogenes can affect hydrogen production. This implies that if one could accurately control the energy flow or the electron flow in the cells, hydrogen productivity would be further greatly improved. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Most enzymes, including protease, play a key role in biotechnology, but their use is quite limited due to poor recovery, limited reusability and instability. Immobilized enzymes offer advantages over free enzymes. This paper reports a simple method for the preparation of immobilized papain, an endolytic cysteine protease (EC: 3.4.22.2), on carboxyl-activated silica nanoparticles.

RESULTS: The carboxyl-activated carriers produced reactive carboxyl groups which then react with the free amino groups of enzyme to give peptide bonds (CONH). The results showed that the thermal and pH stabilities of the immobilized papain were higher than those of free enzyme. And the apparent K_m value of the immobilized papain was 1.26 times higher than that of free enzyme. Moreover, the immobilized papain retained more than 45% of the original activity after ten reuses continuously.

CONCLUSION: The results indicated that papain was successfully immobilized on the surface of the activated carriers. The immobilized papain had not only higher activity recovery, but also better stability, reusability and environmental adaptability. Copyright © 2012 Society of Chemical Industry

BACKGROUND: The adsorption of Cu²⁺ from aqueous solution using crosslinked chitosan hydrogels impregnated with Congo Red (CR) by ion-imprint technology was systematically investigated with particular reference to the effects of contact time, pH, and initial concentration on adsorption.

RESULTS: The adsorption capacity of the crosslinked chitosan without impregnation was only 68.68 mg g⁻¹ for Cu²⁺. However, the adsorption capacity increased from 77.42 (without imprint ion) to 84.54 mg g⁻¹ (imprint ion content 0.5 mmol) after the chitosan was impregnated with a ratio of 1/12 of CR to chitosan. The as-prepared adsorbents were found to be pH-dependent and the process of adsorption agreed well with the Freundlich isotherm. The loaded adsorbents could be regenerated and reused without the appreciable loss of capacity.

CONCLUSION: Chitosan hydrogels impregnated with CR showed higher Cu²⁺ adsorption capacities compared with those prepared conventionally without imprint ion, and thus developed a good approach to increase Cu²⁺ adsorption efficiency in the treatment of waste-water. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Biotrickling filtration could be considered as a suitable and viable technology for controlling the industrial emissions of volatile organic compounds (VOCs) in waste gases. In this study, the performance of a full-scale biotrickling system, including a passively activated carbon-smoothing prefilter was investigated for the treatment of exhaust gases from two different paint spray sources at a furniture facility.

RESULTS: The VOC profiles were uneven for both sources, but the second source was more irregular, with highly variable VOC loads. The plant was operated at empty bed residence times (EBRTs) between 20 and 100 s. The system was able to control the VOC emissions, so air treated could comply with local legal emission limits under suitable operating conditions (EBRT ∼20 s and EBRT ∼85 s for the first and the second source, respectively). Economic evaluation of the treatment, including investment amortization, showed a total cost per 10,000 m³ of treated air of around 8 € and 35 € for the first and the second sources, respectively.

CONCLUSION: The profile, type, and composition of VOC sources were shown to be crucial parameters determining the VOC removal ability and the viability of the biotrickling system. Copyright © 2012 Society of Chemical Industry

BACKGROUND: The catalytic degradation of aqueous Fischer–Tropsch (FT) effluents to fuel gas over Ru/AC has been investigated. In order to understand the catalytic performance and stability of oxide-supported Ru catalysts, several oxide supports (titania, zirconia, γ-alumina and silica) were selected for study, with a focus on the hydrothermal stability of catalysts.

RESULTS: The catalytic efficiency for transforming the oxygenates in aqueous FT effluents to C₁–C₆ alkanes decreased in the order: Ru/ZrO₂∼ Ru/TiO₂ > Ru/SiO₂ > Ru/Al₂O₃. The conversion of alcohols was greatly suppressed over Ru/γ-Al₂O₃. The former two catalysts (Ru/ZrO₂ and Ru/TiO₂) exhibited enhanced efficiency and long-term stability (400 h) relative to Ru/SiO₂ and Ru/Al₂O₃. N₂-physisorption, XRD and SEM showed that titania and zirconia exhibited high structural stability in an aqueous environment. However, the structures of γ-alumina and silica were unstable due to significant drop in surface area and adverse changes in surface morphology. Especially for the case of the Ru/γ-Al₂O₃ catalyst, the γ-alumina was transformed into boehmite structure after reaction, and metal leaching and carbon deposition were extensive.

CONCLUSION: Ru/ZrO₂ or Ru/TiO₂ may be a promising alternative for degrading aqueous FT effluents due to their long-term stability. Copyright © 2012 Society of Chemical Industry

BACKGROUND: This paper describes the results obtained during the thermophilic/mesophilic temperature phased anaerobic digestion (TPAD) of sewage sludge on a pilot scale. The aim of this research study was not only to optimize the anaerobic digestion process, but also to obtain a digested sludge suitable for agricultural applications according to the legal requirements.

RESULTS: Four TPAD assays were carried out: 5/15, 3/15, 3/12 and 3/9 (days/days of solid retention time) with a specific methane production (expressed as LCH₄ g⁻¹ VS_destroyed) of 0.77, 0.83, 0.66 and 0.20, respectively. TPAD 3/15 and 3/12 reached pathogen concentrations of less than 1000 MPN g⁻¹ TS (faecal colifoms) and 3 MPN per 4 g TS (Salmonella spp.); therefore, these digested sludges can be considered Class A biosolids, according to the US Environmental Protection Agency. Concentrations of heavy metals rose after the anaerobic digestion of mixed sludge, but the final values were always below the limits required by legal regulations.

CONCLUSION: TPAD 3/15 is the best option in terms of organic matter removal, CH₄ generation, and process stability. TPAD 3/12 obtained the best final dewaterability and pathogen reduction and in general, showed much better results than those obtained by anaerobic mesophilic control (15 days of SRT). Copyright © 2012 Society of Chemical Industry

BACKGROUND: The aim of this work was to test an innovative packing material (expanded schist) for H₂S biofiltration in order to determine the packing material performance in terms of elimination capacity, removal efficiency and pressure drop changes. Additionally, the changes over time of bed characteristics, especially tortuosity, were evaluated according to porosity measurements.

RESULTS: Schist material can treat large loading rates (up to 30 g.m⁻³.h⁻¹) with 100% efficiency at an empty bed residence time (EBRT) of 16 s, which is much better than most results reported in the literature. The porosity of the packed bed is around 40% (tortuosity estimated to range from 1.5 to 2.0) which leads to pressure drop measurements in the range of 10–80 Pa m⁻¹.

CONCLUSION: Schist is a good material for H₂S biofiltration in terms of mechanical stability, removal efficiency and effective treatment of high H₂S loading rates. Schist is a material that provides the appropriate environment for micro-organisms by itself. This trend should be confirmed over a long period. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Acetals can be considered important bio-based diesel additives. The production of most of these compounds, from an alcohol and an aldehyde, suffers from low conversion due to thermodynamic limitations. These limitations can be overcome through the removal of the by-product water. Previous studies showed that the in situ dehydration options of reactive distillation and pervaporation membrane reactor integration offer little advantage or at least not at reasonable unit dimensions. The aim of the present work is the development of a membrane based process and comparison with other alternatives (based on experimental data).

RESULTS: Three different membrane processes were developed. The one in which the reaction mixture is recycled over a first dehydration membrane module and subsequently through a simple distillation column, was found to give the highest overall conversion (100%) at low recycle rates and reasonable membrane area. This process was techno-economically compared with other possible alternatives: (1) a process based on a conventional tubular reactor and several distillation columns; and (2) a process based on reactive distillation.

CONCLUSIONS: Efficient water removal by membranes avoids possible azeotropes in downstream distillation units making them much simpler, reducing considerably the unit sizes and the energy demand (40% lower). Copyright © 2012 Society of Chemical Industry

BACKGROUND: The antibiotics in industrial and munipical wastewaters could not be removed effectively in conventional anaerobic and aerobic biological treatment plants. Few studies have been performed to investigate the biodegradation and inhibition kinetics of oxytetracycline (OTC) on methanogens and total volatile fatty acids (TVFA).

RESULTS: A high rate anaerobic multichamber bed reactor (AMCBR) was effective in removing the molasses-chemical oxygen demand (COD), and the OTC antibiotic with yields as high as 96% at an influent OTC loading rate of 133.33 gOTC m⁻³ day⁻¹ at a hydraulic retention time (HRT) of 2.25 days. Increasing the OTC loading rates from 22.22 gOTC m⁻³ day⁻¹ to 133.33 gOTC m⁻³ day⁻¹ improved both hydrolysis and specific utilization of molasses-COD. The inhibition constants of TVFA (K_{I−TVFA−meth}) and OTC (K_{I−OTC−meth}) on methanogens decreased at OTC loadings > 133.33 gOTC m⁻³ day⁻¹. The direct effect of OTC loadings > 133.3 gOTC m⁻³ day⁻¹ on acidogens and methanogens was evaluated using the Haldane inhibition kinetic.

CONCLUSION: OTC antibiotic was effectively removed in a sequential AMCBR/completely stirred tank reactor (CSTR). The Haldane inhibition constant (K_ID) decreased significantly at high OTC loads indicating the increase in toxicity. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Owing to the rapid depletion of petroleum fuel, the production of bio-butanol has attracted much attention. However, low butanol productivity severely limits its potential industrial application. It is important to establish an approach for recovering low-concentration butanol from fermentation broth. Experiments were conducted using batch adsorption mode under different conditions of initial butanol concentration and temperature. Batch adsorption data were fitted to Langmuir and Freundlich isotherms and the macropore diffusion, pseudo-first- and second-order models for kinetic study.

RESULTS: The maximum adsorption capacity of butanol onto KA-I resin increase with increasing temperature, ranged from 139.836 to 304.397 mg g⁻¹. The equilibrium adsorption data were well fitted by the Langmuir isotherm. The adsorption kinetics was more accurately represented by the macropore diffusion model, which also clearly predicted the intraparticle distribution of the concentration. The effective pore diffusivity (D_p) was dependent upon temperature, but independent of initial butanol concentration, and was 0.251 × 10⁻¹⁰, 0.73 × 10⁻¹⁰, 1.32 × 10⁻¹⁰ and 4.31 × 10⁻¹⁰ m² s⁻¹ at 283.13, 293.13, 303.13 and 310.13 K, respectively.

CONCLUSION: This work demonstrates that KA-I resin is an efficient adsorbent for the removal of butanol from aqueous solutions and available for practical applications for future in situ product recovery of butanol from ABE fermentation broth. Copyright © 2012 Society of Chemical Industry

BACKGROUND: The performance of two biotrickling filters (BTFs) was evaluated for styrene removal from gas streams at the start-up period and at a pseudo-steady-state under various operating conditions.

RESULTS: The BTFs exceeded 99% removal efficiency within 19 days when the average inlet styrene concentration was 250 mg m⁻³ and gas empty bed retention time (EBCT) was 30.0 s. The effect of a surfactant, Triton X-100, on styrene removal was examined by comparative experiments in which one biofilter was fed with nutrient solution with the surfactant while the other without the surfactant, and the average organic loading rate of styrene was set at 65.3, 100.9 and 201.7 g styrene m⁻³ h⁻¹, respectively. Results showed that the corresponding average removal efficiency was 87%, 70% and 50% for the BTF without surfactant, while the average removal efficiency for the BTF with surfactant was 96%, 92% and 82%. Excessive biomass accumulation was observed in the medium when the styrene loading rate was high. However, the biomass density within the BTF medium when the surfactant was added remained stable during the whole period of the operation.

CONCLUSION: These results demonstrated that the use of Triton X-100 can improve the degradation of styrene and control the excessive biomass accumulation. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Ethanol production from synthesis gas (syngas) by Clostridium ljungdahlii was autotrophically carried out in a continuous flow stirred tank bioreactor (CSTR). A 2 L bioreactor was operated at 37 °C and constant agitation rate of 500 rpm. The experiments were conducted at various media flow rates and uncontrolled culture pH condition while the gas flow rate was kept constant at 14 mL min⁻¹.

RESULTS: Continuous fermentation of the syngas containing 55% CO, 20% H₂, 10% CO₂ and 15% argon as internal standard resulted in cell dry weight of 2.34 g L⁻¹ and CO conversion of 93%. Maximum concentration of ethanol and acetate was 6.50 g EthOH L⁻¹ and 5.43 g Ac L⁻¹.

CONCLUSION: High ethanol concentration was achieved in continuous fermentation using C. ljungdahlii. The ethanol producing ability of this acetogene and succesful switch of the metabolic pathway from acetogenesis to solventogenesis during the fermentation process was confirmed. Copyright © 2012 Society of Chemical Industry

The development of industrial microbial processes is gaining unprecedented momentum. Increased concern for environmental issues and the prospect of declining petroleum resources has shifted the industrial focus increasingly to microorganisms as biocatalysts. At the same time systems biology and synthetic biology supply industry and academia with new tools to design optimal microbial cell factories.

Among the tools are systems biology approaches allowing the modelling of cellular networks for rational strain design, single cell analyses methods for gaining insight into population hetereogeneity, and an exciting combination of tools from structural biology and synthetic biology, permitting the catalysis of new (unnatural) enzymatic reactions or the production of new (unnatural) chemicals.

This perspective article outlines recent advances and new developments within the field of microbial cell factory design. Copyright © 2012 Society of Chemical Industry

BACKGROUND: A three-liquid-phase system (TLPS) composed of an organic solvent-rich top phase, a polymer-rich middle phase and a salt-rich bottom phase is a newly emerging separation medium. Due to low affinity of the polymer-rich phase for metals it is necessary and important to search for a suitable complexing agent that has a definite affinity for the polymer-rich middle phase and a high selectivity for the metal ion of interest.

RESULTS: Addition of 1,10-phenanthroline (phen) is effective in enhancing the separation of titanium and iron from magnesium in the TLPS consisting of trialkylphosphine oxide (TRPO)-PEG 2000-(NH₄)₂SO₄. Hydrogen-bonding interactions between PEG 2000 and phen molecules are the driving force for anchoring tri(phen)-iron(II) sulfate complexes in the middle phase. Under the conditions (pH = 1.5, molar ratio of phen to iron(II) = 3.4:1), nearly 86% of titanium was extracted into the top phase while 100% of iron(II) was distributed in the middle phase, without any interference between the metal species. The separation factor of titanium and iron in the upper two phases was greater than 20 000.

CONCLUSIONS: A single step of extraction and separation of titanium and iron from magnesium was realized in the TRPO-PEG 2000-(NH₄)₂SO₄ TLPS with phen as additive. It highlights the effectiveness of TLPS in dealing with multi-metal solutions and suggests a potential use of TLPS in the separation of iron and other target metals. As iron is ubiquitous the separation of iron is often needed in both analytical processes and the hydrometallurgical industry. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Technologies based on aerobic granular biomass are presented as a new alternative application to wastewater treatment due to its advantages in comparison with the conventional activated sludge processes. However, the properties of the aerobic granules can be influenced by the presence of residual amounts of coagulant-flocculant reagents, frequently used as pre-treatment before the biological process. In this work the effect of these compounds on aerobic granular biomass development was tested.

RESULTS: The presence of coagulant-flocculant reagents led to a worse biomass retention capacity with a lower VSS concentration compared with a control reactor (4.5 vs. 7.9 g VSS L⁻¹) and with a higher SVI (70 vs. 40 mL [g TSS]⁻¹) and diameter (5.0 vs. 2.3 mm). These reagents also caused a decrease in the maximum oxygen consumption rate, but the removal efficiencies of organic matter (90%) and nitrogen (60%) achieved were similar to those in the control reactor.

CONCLUSION: The continuous presence of residual levels of coagulant-flocculant reagents from the pre-treatment unit negatively affected the formation process and the physical properties of the aerobic granules; however, the removal of organic matter and nitrogen were not affected. Copyright © 2012 Society of Chemical Industry

BACKGROUND: In this study the effects of the addition of emulsified polydimethylsiloxane (PMDS) FG-10 on the oxygen transfer coefficient (k_La) of submerged cultures of Staphylococcus warneri EX17 and its lipase production is described. FG-10 is an emulsified silicone capable of dissolving 50 times more oxygen than water. The combined effects of FG-10 concentration and different conditions of agitation were optimized in bioreactors using statistical design tools, and the cultures were run using raw glycerol from biodiesel synthesis as the sole carbon source.

RESULTS: The optimal conditions found to improve lipase production were FG-10 concentration of 11.2% (v/v) and speed agitation of 527 rpm, respectively, producing around 861 U L⁻¹ of lipolytic activity, a maximal cell concentration of 8.4 g L⁻¹, and a k_La of 99 h⁻¹, values that are approximately 3 times higher than cultures without FG-10.

CONCLUSIONS: This is the first report in the literature on the use of this class of chemicals as oxygen carriers in microbial cultures and its effect on k_La and lipase production, demonstrating the potential use of FG-10 in microbial cultures. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Environmental pollution and its abatement have attracted much attention for some time. The problem of removing pollutants from water and wastewater has grown along with rapid industrialization. Formaldehyde polymerized banana stem (FPBS) having sulphonic acid groups was investigated as an adsorbent for cadmium(II) removal from aqueous solutions.

RESULTS: The outstanding function of the adsorbent was demonstrated at pH 9.0. The adsorption efficiency of FPBS was compared with BS and results showed that FPBS was two times more effective than BS for cadmium(II) removal. Maximum recoveries of 97.3 and 90.3% for 10 and 25 mg L⁻¹ initial concentrations were obtained at pH 9.0. Kinetic studies revealed that adsorption occurred in two stages: external mass transport in the first stage and intra-particular diffusion in the second stage. Adsorption was found to be rapid and equilibrium was attained in 60 min. Among the various desorbing agents tested, 99.2% cadmium recovery was achieved with 0.1 mol L⁻¹ HCl.

CONCLUSIONS: The uptake efficiency of cadmium(II) by FPBS was determined. Repeated adsorption-desorption study showed that FPBS can be used as an adsorbent for the removal and recovery of Cd(II) from aqueous solutions. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Heterogeneous Fenton catalysts have been used to treat various organic pollutants in an aqueous environment. The present study has investigated the degradation of 2,4-dinitrophenol (2,4-DNP), a priority pollutant generated by such industries as pharmaceuticals, pesticides, pigments and dyes. Degradation of 2,4-DNP (100 mg L⁻¹) was studied using Fe³⁺ loaded on Al₂O₃ as a heterogeneous catalyst in the presence of H₂O₂, and the efficiency compared with the homogeneous Fe³⁺/H₂O₂ based Fenton-like process. The effect of different parameters for both processes, such as catalyst loading, H₂O₂ concentration, initial solution pH, initial substrate concentration and temperature were investigated and the optimum operating conditions determined.

RESULTS: Under optimal operating conditions of the homogeneous system ([Fe³⁺] 125 mg L⁻¹; [H₂O₂] 250 mg L⁻¹; pH 3; room temperature), 92.5% degradation was achieved in 35 min for an initial 2,4-DNP concentration of 100 mg L⁻¹. In the case of immobilized Fe (Fe³⁺–Al₂O₃ catalyst), degradation improved to 98.7% under the condition 10 wt% [Fe³⁺–Al₂O₃] 1 g L⁻¹ catalyst loading; [H₂O₂] 250 mg L⁻¹; pH 3; at room temperature for the same duration.

CONCLUSIONS: This study demonstrated the stability and reusability of the prepared heterogeneous catalyst. This process is a viable technique for treatment of aqueous solutions containing contaminants. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Mycelium of the medicinal mushroom shiitake, Lentinus edodes, is a potential source for production of the blood cholesterol reducing compound eritadenine. To increase the mycelial biomass and in turn the production of eritadenine, a potential growth promoting substance in the form of a water extract of distillers dried grains with solubles (DDGS) was added to the culture media.

RESULTS: The hot water extract of DDGS was shown to considerably increase the growth of shiitake mycelia in bioreactor cultivations; the mycelial yield was 2–3 times higher than in the control, and the highest final biomass concentration obtained was 3.4 g L⁻¹. Further, by using shake flask cultures as inoculums the bioreactor cultivation time could be reduced by 1 week for some of the experiments. The highest final titer of eritadenine in the present study was 25.1 mg L⁻¹, which was about 2 times higher than in the control, and was also obtained when a water extract of DDGS was added to the culture medium.

CONCLUSION: It was demonstrated that a water extract of DDGS promoted the growth of shiitake mycelia in bioreactor cultivations, along with enhanced eritadenine production. Copyright © 2012 Society of Chemical Industry

BACKGROUND: The objectives of this study were optimization of silver nanoparticle synthesis using biotransformations by Lactobacillus casei subsp. casei, and studying the location of nanoparticles synthesis in this microorganism.

RESULTS: The presence of AgNO₃ (0.1 mmol L⁻¹) in the culture as the enzyme inducer, and glucose (56 mmol L⁻¹) as the electron donor in the reaction mixture had positive effects on nanoparticle production. By gradually increasing the concentration of AgNO₃ (as the substrate) to 6 mmol L⁻¹, nanoparticle production was increased. By increasing biomass, nanoparticles production was also increased. Biosynthesized silver nanoparticles were almost spherical, single (25–50 nm) or in aggregates (100 nm), attached to the surface of biomass or were inside and outside of the cells.

CONCLUSION: The present study demonstrated the bioreductive synthesis of silver nanoparticles using L. casei subsp. casei at room temperature. In this research, and due to experience in optimization of biotransformation reactions, the reaction conditions were successfully optimized to increase the yield of nanoparticles production and productivity of this biosynthetic approach. Copyright © 2012 Society of Chemical Industry

BACKGROUND: This paper reports on process synthesis and economics of combined methanol and CHP (combined heat and power) energy production from crude biooil, waste glycerol produced in biodiesel factories and biomass wastes using integrated reactor design for hydrogen rich syngas. This new process consists of three process steps: (a) pyrolysis of organic waste material to produce biooil, char and pyrogas; (b) steam assisted hydrogasification of the crude glycerol wastes, biooil mixed with pyrogas for hydrogen rich gas; and (c) a low temperature methanol synthesis process. The H₂-rich gas remaining after methanol synthesis is recycled back to the pyrolysis reactor, the catalytic hydro-gasification process and the heat recovery steam generator (HRSG).

RESULTS: The breakeven price of the Hbiomethanol process yields positive net financial NPV and IRR above 600 USD per tonne. The total capital cost for a small-scale methanol plant of capacity 2 tonne h⁻¹ combined with a cogeneration plant of capacity 2 MWe power is estimated to be 170.5 million USD.

CONCLUSION: Recycling gas allows the methanol synthesis reactor to perform at a relatively lower pressure than conventionally while the plant still maintains a high methanol yield. The integrated hydrogasification reactor and energy recovery design process minimizes heat loss and increases the process thermal efficiency. The Hbiomethanol process can convert any condensed carbonaceous material and liquid wastes, to produce methanol and CHP. Copyright © 2012 Society of Chemical Industry

Alkali-dissolution pretreatment of softwood spruce and hardwood birch to improve ethanol and biogas production was investigated. The pretreatments were carried out at different temperatures between − 15 and 80 °C with NaOH/thiourea (7/5.5 wt%), NaOH/urea (7/12 wt%), NaOH/urea/thiourea (7/8/6.5 wt%), and NaOH/PEG (7/1 wt%) aqueous solutions. The pretreated materials were then subjected to enzymatic hydrolysis for 72 h. The pretreatments by NaOH/thiourea at − 15 °C improved the hydrolysis yields of spruce from 11.7% to 57% of theoretical yield, and for birch from 23.1% to 83% of theoretical yield. The enzymatic hydrolysis and fermentation of these pretreated materials by NaOH/thiourea with baker's yeast resulted in 54.0% of theoretical yield compared with 10.9% for untreated spruce and 80.9% of theoretical yield compared with 12.9% for untreated birch. Furthermore, anaerobic digestion of pretreated materials resulted in 0.36 L g⁻¹ VS methane compared with 0.23 L g⁻¹ VS for untreated birch, and 0.21 L g⁻¹ VS compared with 0.03 L g⁻¹ VS for untreated spruce. Copyright © 2012 Society of Chemical Industry

BACKGROUND: The ASM3 extended for two-step nitrification–denitrification represents the most accurate model for the description of the activated sludge process with nitrate bypass nitrification–denitrification. This model includes 20 reaction rates, 15 state variables, and more than 35 parameters, which make its calculation costly and difficult to estimate. The lack of a fast and accurate model able to predict both concentration of nitrite and nitrate over time is the principal obstacle for efficient model-based optimization and model-based control.

RESULTS: In this work, a fast and accurate model for the activated sludge process in a sequencing batch reactor is proposed. For this purpose, the ASM3 extended for two-step nitrification–denitrification, a 15-state variable model built for a general description of the ASP, is reduced to match the specific conditions of sequencing batch reactor systems with shortcut biological nitrogen removal to a nine-state model and then further to a six-state and five-state model under appropriate assumptions. The proposed model maintains the two-step nitrification–denitrification process feature of the original model and can thus describe the bypass of nitrate, showing increased tractability and lower computer costs. Different approaches for model reduction together with an exhaustive analysis of the extended ASM3 model as well as the process are discussed.

CONCLUSIONS: The resulting model with only five differential equations reduces the calculation time by up to one order of magnitude, while maintaining a high description accuracy, demonstrating the advantages of model reduction. Copyright © 2012 Society of Chemical Industry

BACKGROUND: The piggery industry is important both worldwide and in Canada, but localized production of large quantities of swine slurry causes severe environmental problems such as aquatic pollution and greenhouse gas emissions. The main objective of this study was to determine whether it is possible to simultaneously treat methane (CH₄) and swine slurry using an inorganic biofilter.

RESULTS: A novel biofilter was designed to overcome the inhibition of CH₄ biodegradation by swine slurry. The CH₄ elimination capacity increased with the inlet load and a maximum value of 18.8 ± 1.0 g m⁻³ h⁻¹ was obtained at an inlet load of 46.7 ± 0.9 g m⁻³ h⁻¹ and a CH₄ concentration of 3.3 g m⁻³. Four pure strains of fungi were used in an attempt to improve the removal of CH₄, but no significant effect was observed. Between 0.35 and 3.4 g m⁻³, the CH₄ concentration had no effect on swine slurry treatment with removal efficiencies of 67 ± 10% for organic carbon and 70 ± 7% for ammonium. The influence of the slurry supply was analyzed and the best results were obtained with a supply method of six doses of 50 mL per day.

CONCLUSION: Even though the results were lower than those obtained for the biofiltration of CH₄ alone, this study demonstrated the feasibility of treating CH₄ and swine slurry with the same biofilter using a novel design. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Poly(HEMA-co-MMA) beads were prepared from 2-hydroxyethyl-methacrylate (HEMA) and methylmethacrylate (MMA) in the presence of FeCl₃. Thermal co-precipitation of Fe(III) ions containing beads with Fe(II) ions was carried out under alkaline conditions. The magnetic beads were grafted with poly(glycidylmethacrylate; p(GMA)), and the epoxy groups of the grafted p(GMA) brushes were converted into amino groups by reaction with ammonia.

RESULTS: The magnetic beads were characterized by surface area measurement, electron spin resonance (ESR), Mössbauer spectroscopy and scanning electron microscopy (SEM). The maximum adsorption of Reactive Green-19 (RG-19) dye on the p(GMA) grafted and amine modified magnetic beads was around pH 3.0. The adsorption capacity of magnetic beads was 84.6 mg dye g⁻¹. The effects of adsorbent dosage, ionic strength and temperature have also been reported. Batch kinetic sorption experiments showed that a pseudo-second-order rate kinetic model was applicable.

CONCLUSION: The p(GMA) grafted and amine modified magnetic beads (adsorbent) were expected to have the advantage of mobility of the grafted chains in the removal of acidic dyes from aqueous solutions. The magnetic beads have potential as an adsorbent for removal of pollutants under various experimental conditions without significant reduction in their initial adsorption capacity. Copyright © 2011 Society of Chemical Industry

BACKROUND: In Izmir, Turkey, wastewaters from the petrochemical industry are treated using conventional activated sludge systems. A significant proportion of poly-aromatic hydrocarbons (PAHs) with high-molecular weights remains in this treatment system and inhibits the biological activity. Biosurfactants increase PAHs degradation by enhancing the solubility of the petroleum components. The aerobic inhibition kinetics of PAHs has not previously been investigated in the presence of biosurfactants for a real petrochemical industry wastewater.

RESULTS: Among the kinetic models used (Monod-type, zero, first-order and second-order) it was found that the Monod kinetic was effective for describing the biodegradation of PAHs in petrochemcal industry wastewater in the presence of three biosurfactants, namely Rhamnolipid (RD), Surfactine (SR) and Emulsan (EM) in an aerobic activated sludge reactor (AASR). The maximum PAH removal rate (R_max) and specific growth rate of PAH degrading bacteria (µ_max) increased, while the half saturation concentration of PAH (K_s) decreased at 15 mg L⁻¹ RD concentration compared with the control without biosurfactant at a sludge retention time (SRT) of 25 days.

CONCLUSION: PAH oxidation is typified by competitive inhibition at RD concentrations > 15 mg L⁻¹ resulting in increases in K_s values with PAH accumulation. Low inhibition constant (K_ID) values reflect difficulties in the metabolizability of PAHs. Metabolite production decreased at RD = 25 mg L⁻¹ in the PAHs indeno (1,2,3-cd) pyrene (IcdP), flourene (FLN), phenanthrene (PHE) and benzo(a)pyrene (BaP). Copyright © 2011 Society of Chemical Industry

BACKGROUND: The adsorption of Cu(II) on β-cyclodextrin (β-CD) modified multiwall carbon nanotubes/iron oxides (denoted as MWCNT/IO/CD) as a function of contact time, pH, adsorbent content, temperature, fulvic acid (FA) and initial Cu(II) concentrations was investigated using a batch technique under ambient conditions.

RESULTS: The adsorption of Cu(II) was strongly dependent on pH, adsorbent content, temperature and FA. A positive effect of FA on Cu(II) adsorption was found at pH < 6.5, whereas a negative effect was observed at pH > 6.5. Different effects of FA/Cu(II) concentrations on Cu(II) and FA adsorption were observed, indicating enhanced Cu(II) adsorption on FA bound MWCNT/IO/CD, whereas FA adsorption was decreased in the presence of Cu(II) ions. The adsorption isotherms were well fitted by the linear isotherm model. The adsorption thermodynamic parameters calculated from temperature dependent adsorption isotherms suggested that the adsorption of Cu(II) on MWCNT/IO/CD was an endothermic and spontaneous process.

CONCLUSIONS: MWCNT/IO/CD is a promising magnetic material for the preconcentration and separation of Cu(II) ions from aqueous solutions in environmental pollution cleanup. Copyright © 2011 Society of Chemical Industry

BACKGROUND: Hydrogen sulphide (H₂S) present in biogas can be oxidized to elemental sulphur (S₀) or sulphate (SO₄²⁻) using nitrate and nitrite. Both nitrate and nitrite are normally available in most wastewater treatment plants and could be used to oxidize H₂S depending on the molar loading ratio of wastewater and biogas. A control approach is required in order to minimize the fluctuations in inlet and outlet H₂S concentrations in biogas, and the oxidation potential of the wastewater used.

RESULTS: A control scheme has been developed for biogas desulphurization using oxidation reduction potential under industrial conditions. The redox potential was maintained at about + 50 to + 100 mV in the activated sludge plant to monitor the performance of the nitrification process. The redox potential in the bioscrubber was related to sulphide removal from biogas. More than 90% of the hydrogen sulphide was removed from the biogas.

CONCLUSION: The oxidation reduction potential can be used as a key parameter for monitoring and controlling biogas cleaning. Fluctuations of the inlet H₂S concentration in biogas can be compensated by manipulating the flowrates of wastewater used in order to achieve consistent and desired H₂S concentrations in treated biogas. Copyright © 2011 Society of Chemical Industry

BACKGROUND: Production of bioethanol from wood using concentrated acid hydrolysis has received less attention than the dilute acid hydrolysis route. The feasibility of producing lignocellulosic bioethanol from spruce and birch via concentrated acid hydrolysis was studied experimentally. Hydrolysis with sulfuric acid, chromatographic purification of the hydrolysate, and fermentation of the monosaccharides were investigated.

RESULTS: Monosaccharide yields of 70% were obtained in the hydrolysis of spruce and birch. Only low amounts of by-products were formed. With chromatographic purification of the hydrolysate, over 90% of the hydrolysis acid was recovered for recycling, and furfural and HMF were removed completely. Most of the acetic acid was recovered in a separate fraction. The monosaccharide yield in a single pass separation was approximately 70%. In the fermentation, S. cerevisiae produced higher amounts of ethanol and more efficiently than P. stipitis. Chromatographically purified hydrolysates gave higher ethanol productivities and yields than Ca(OH)₂ neutralized hydrolysates.

CONCLUSIONS: Chromatographic purification of concentrated acid lignocellulosic hydrolysates has advantages when compared with neutralization with Ca(OH)₂. With chromatography, most of the inhibitory compounds can be removed from the hydrolysates. In addition, due to the recycling of the hydrolysis acid, the economy of the bioethanol manufacturing process is increased considerably. Copyright © 2011 Society of Chemical Industry

BACKGROUND: The effects of shear rate induced molecular orientation in polymeric based asymmetric membranes on performance, structural details, key properties, morphologies and pore size distribution were studied. Asymmetric membranes fabricated at five different potential shear rates ranging from 93.33–466.67 s⁻¹ were evaluated based on nanofiltration test. The use of Spiegler–Kedem, steric-hindrance pore and Teorell–Meyers–Sievers models enables an assessment to be made of the relationship between shear rates and membranes properties.

RESULTS: Experimental and modeling results show that there is a significant correlation between shear and membrane characteristics, whereby as shear rate increases, the separation performances of nanofiltration membranes increase until an optimum (critical) level of shear is achieved. Beyond the optimum shear, the deterioration in membrane performance suggests that there exists an optimum shear rate which produces optimal structural details, key properties, morphologies and pore size distributions.

CONCLUSIONS: Results showed that a skinned-oriented highly selective charged asymmetric low pressure nanofiltration (ALP-NF) membrane was successfully developed. The optimum shear rate (critical shear) was found to be 233.33 s⁻¹. At the optimum shear rate, the fabricated ALP-NF membranes produced the finest properties, morphology and narrowest pore distributions. The positive improvement in performance properties of ALP-NF membrane provides the potential for producing a highly selective NF membrane for different applications in the future. Copyright © 2011 Society of Chemical Industry

BACKGROUND: Water-soluble reactive azo dyes are the most problematic dye house effluents, as they tend to pass through conventional treatment systems unaffected. The release of these compounds into the environment is undesirable and their removal becomes environmentally important. In this work, synthesis, characterization and sorption properties of hydotalcite-like compounds (Mg/Al and Mg/Fe), calcined and uncalcined, were investigated for the removal of the reactive azo dye Remazol Red 3BS.

RESULTS: The calcined compounds present higher surface area than the uncalcined. The optimum pH for sorption was found to be 6. Thermodynamic analysis reveals that the sorption is spontaneous and endothermic. Equilibrium data were fitted by a Langmuir model, and kinetic data by a second-order model. The calcined Mg/Al compound showed the highest sorption capacity, at 0.125 mmol g⁻¹. Regeneration of dye loaded derivative is achieved using the surfactant SDS.

CONCLUSIONS: The prepared hydotalcite-like compounds and especially calcined Mg-Al exhibited significant adsorption capacity, kinetics, and regenerative ability. Its potential applicability as sorbent should be tested in a large-scale implementation. Copyright © 2011 Society of Chemical Industry

BACKGROUND: The removal of antibiotic ampicillin sodium using H₂O₂ and modified granular activated carbon (GAC) is discussed. Two types of modified activated carbons were used in experiment to catalyze ·OH production from H₂O₂. One was modified with base (NaOH; called B-GAC), the other was modified with Fe(NO₃)₃ (Fe-GAC) and the nominal Fe metal loading was 5 wt%. In the experiment, pH, contact time, dosage of activated carbon and H₂O₂ and initial concentration of ampicillin sodium were investigated to determine their influence on the removal efficiency. The stability of Fe-GAC was also evaluated.

RESULTS: With an initial ampicillin sodium concentration of 200 mg L⁻¹, 85.2% of chemical oxygen demand (COD) and 76.4% of total organic carbon (TOC) can be removed with 8.0 g L⁻¹ of B-GAC and 80 mg L⁻¹ of H₂O₂ (at pH 5.0). For the Fe-GAC/H₂O₂ process, with 5.0 g L⁻¹ of activated carbon and 80 mg L⁻¹ of H₂O₂, COD and TOC removal can be elevated to 91.2% and 79.5% (at pH 3.0), respectively.

CONCLUSION: The integration of activated carbon and H₂O₂ treatment was more effective for the removal of ampicillin from aqueous solution than using activated carbon alone. In the process, adsorption played a dominant role and the addition of a small amount of H₂O₂ accelerated the reaction rate and improved the removal efficiency. pH also greatly affected removal efficiency. Copyright © 2011 Society of Chemical Industry

BACKGROUND: This paper describes a convenient and effective strategy to construct a highly sensitive amperometric biosensor for nitrite (NO₂⁻) and hydrogen peroxide (H₂O₂). First, Pt nanoparticles (PtNPs) were electrodeposited on a glassy carbon electrode (GCE) surface, which promoted electron transfer and enhanced the loading of poly-thionine (PTH). Subsequently, thionine (TH) was electropolymerized on the PtNPs/GCE, and gold nanoparticles (AuNPs) were assembled onto the PTH film to improve the absorption capacity of hemoglobin (Hb) and further facilitate electron transfer. Finally, Hb was immobilized onto the electrode through the AuNPs.

RESULTS: Cyclic voltammetry (CV) and scanning electron microscopy (SEM) were used to characterize the fabrication process of the sensing surface. Under optimum conditions, the biosensors can be used for the determination of NO₂⁻ in the concentration range 70 nmol L⁻¹ to 1.2 mmo L⁻¹ and of H₂O₂ in the range 4.9 µmol L⁻¹ to 6.8 mmol L⁻¹. The detection limits (S/N = 3) were 20 nmol L⁻¹ and 1.4 µmol L⁻¹, respectively.

CONCLUSION: The biosensor exhibits good analytical performance, acceptable stability and good selectivity. Copyright © 2011 Society of Chemical Industry

BACKGROUND: There are few reports on erythromycin molecularly imprinted polymers (MIPs) used as HPLC stationary phase and solid phase extraction matrices. These imprinted polymers are prepared by bulk polymerization, which is tedious and time-consuming, and they are irregular and possess poor reproducibility and low binding capacity. In this study, molecularly imprinted microspheres for erythromycin were prepared by aqueous suspension polymerization for the first time.

RESULTS: Imprinted microspheres for erythromycin were prepared using suspension polymerization in which 1.5% PVA-water solution is used as continuous phase, and chloroform solution containing erythromycin, methacrylic acid and crosslinker is used as disperse phase. The composition of disperse phase is optimized, and the optimum molar ratio of erythromycin to methacrylic acid was 1:5. Selectivity analysis revealed that the imprinted microspheres can specifically recognize erythromycin from its structure analogues. The binding mechanism between erythromycin and methacrylic acid was investigated by UV-Vis spectrophotometry. Adsorption kinetics and the adsorption isotherm of the imprinted microspheres indicate that erythromycin can be adsorbed rapidly by the imprinted microspheres and the maximum theoretical static binding capacity is 128.6110 mg g⁻¹. The imprinted microspheres were used to extract erythromycin from a milk sample and a high recovery rate was obtained.

CONCLUSION: Molecularly imprinted microspheres for erythromycin were uniform and possess high adsorption capacity and excellent selectivity. They are therefore a promising extraction and chromatographic media. Copyright © 2011 Society of Chemical Industry

BACKGROUND:Chlorella strains rather than terrestrial oil crops having higher oil content and shorter generation time have been considered as promising candidates for alternative biodiesel. Since the influence of light quality on oil formation of microalgae in either monoculture or mixed culture has been shown to be either inconsistent or ambiguous, a light-emitting diode (LED) photo-bioreactor with different light sources and intensities was used in this study to investigate a cost-effective lipid production process.

RESULTS: The oil accumulation in a mixed culture of Chlorella sp. and Saccharomyces cerevisiae was higher than that in the monoculture under the different light sources used. Results of the influence of light quality on the mixed culture indicated that the optimal light wavelength and intensity for biomass formation was red LED light at 1000 lux, whereas the optimum for oil formation was blue LED light at 1000 lux. A novel two-stage LED photo-bioreactor was thus proposed and the highest P_max and productivity in this study were obtained as 261 mg L⁻¹ and 8.16 mg L⁻¹ h⁻¹, respectively.

CONCLUSION: A novel two-stage LED photo-bioreactor using a mixed culture to optimize microalgal oil production was proposed and successfully demonstrated in this study. Copyright © 2011 Society of Chemical Industry

BACKGROUND:Yarrowia lipolytica lipase LIP2 (YlLIP2) is an important industrial enzyme that has many potential applications. Although it has been successfully expressed in Pichia pastoris under the control of the AOX1 promoter (pAOX1), there have been many efforts to develop new alternative promoters to pAOX1 in order to avoid using methanol in the fermentation. Investigation of YlLIP2 production in P. pastoris using the formaldehyde dehydrogenase 1 promoter (pFLD1) is especially attractive, since little is known about its application in methanol-free culture strategies.

RESULTS: Three fed-batch cultivations were performed to investigate the production of YlLIP2 in a pFLD1-based system. When methanol was used as the fed-batch feeding substrate, the maximum YlLIP2 activity obtained in a 10-L bioreactor was 30 000 U mL⁻¹ after 143 h of culture, whereas the maximum YlLIP2 activity was further increased to 35 000 U mL⁻¹ by adopting a co-induction strategy with methanol and methylamine as a mixed fed-batch substrate. Furthermore, the maximum YlLIP2 activity reached 13 000 U mL⁻¹ after 80 h of cultivation in a methanol-free culture.

CONCLUSION: The expression levels of YlLIP2 in the pFLD1-based system were comparable with those in a pAOX1-based system. The results suggest that pFLD1 is an attractive alternative to pAOX1, and may make it feasible to induce high yields of protein expression. Copyright © 2011 Society of Chemical Industry

BACKGROUND: As a new protein expression and self-immobilization system, cell-surface displayed enzymes have attracted increasing attention. In this study, Geotrichum sp. lipase (GSL), an important enzyme for the enrichment of polyunsaturated fatty acids (PUFAs), was first displayed on the cell surface of Saccharomyces cerevisiae.

RESULTS: The activity of displayed GSL was higher (43.7 U g⁻¹ dry cell) than that of Candida antarctica lipase B (26.26 U g⁻¹ dry cell) and that of Rhizopus oryzae lipase (4.1 U g⁻¹ dry cell). It also exhibited higher thermostability than the free lipase, and retained 89% of the original activity after incubation at 40 °C for 3 h, compared with 48% at 35 °C for the free lipase at pH 8.5. Interestingly, the displayed lipase had a wider pH range and better pH stability. It had higher activity at all pH values than the free GSL, and retained 86% of the original activity in the pH range 9.5 to 10.5, whereas the activity of the free GSL could not be detected at pH 10.

CONCLUSION: This work presented a method to prepare a whole-cell biocatalyst with better stability and broader pH tolerance which will provide a useful strategy for other cost-effective self-immobilized industrial lipases. Copyright © 2011 Society of Chemical Industry

BACKGROUND: In order to effectively degrade bovine serum albumin (BSA) under ultrasonic irradiation, biological mineral material (tooth powder) was adopted to mix with nano-sized TiO₂ powder. A TiO₂/tooth composite with high sonocatalytic activity and remarkable selectivity was prepared.

RESULTS: TiO₂/tooth composite with tooth content of 30% (w/w) heat-treated at 500 °C for 40 min was used as sonocatalyst and the catalytic degradation of BSA under ultrasonic irradiation was examined. Some influencing factors, such as ultrasonic irradiation time, TiO₂/tooth catalyst amount, solution acidity and NaCl concentration, were studied by UV-vis and fluorescence spectroscopic analysis. Furthermore, the BSA attack site for the TiO₂/tooth composite was identifies by synchronous fluorescence spectra.

CONCLUSION: The results indicated that, under ultrasonic irradiation, the TiO₂/tooth composite can promote the degradation of BSA more effectively than pure nano-sized TiO₂ powder. The attack site is identified as tyrosine (Tyr) residue. These results are of great significance for the use of a sonocatalytic method to treat tumours in clinical applications. Copyright © 2011 Society of Chemical Industry

The objective of this study was to evaluate the influence of moisture content on the specific methanogenic activity (SMA) of a fresh dry mesophilic digestate from a municipal solid waste digester plant. For this purpose, SMA tests were performed under mesophilic conditions in 500 mL glass bottles of volume used as batch reactors, during a period of 20–25 days. Cellulose, propionate and acetate were used as substrates (5 g_COD kg⁻¹ digestate) at four different moisture contents, ranging from 65 to 82%. The moisture content strongly influenced the specific methanogenic activity. The highest SMA values were observed at a moisture content of 82% (11.1, 7.8 and 6.0 mg_COD g_VS⁻¹ d⁻¹ for cellulose, propionate and acetate spikes, respectively). SMA and moisture content were found to be linearly linked. Dry digestion at low water content is thus detrimental to the biological activity, probably due to physical limitations. Copyright © 2011 Society of Chemical Industry

Fumaric acid (FA) was produced from Eucalyptus globulus wood by successive steps of hydrothermal processing (to solubilize hemicelluloses and to increase the susceptibility of solids to enzymatic hydrolysis), enzymatic hydrolysis and fermentation with Rhizopus arrhizus DSM 5772. For comparative purposes, additional fermentations were carried out using synthetic media. Single stage fermentation of synthetic media led to a medium containing 11.8 g FA L⁻¹ (Y_P/S = 0.60 g g⁻¹). Operating in fed batch mode, the fourth stage increased the FA concentration from 19.7 up to 43.6 g L⁻¹ (Y_P/S = 0.71 g g⁻¹). Hydrolyzate fermentation in a single stage resulted in lower fumaric acid concentration (9.65 g L⁻¹) and yield (0.35 g g⁻¹). Additional fermentations were carried out in media made with hydrolyzates subjected to membrane processing, adsorption or ion exchange. The highest yield (Y_P/S = 0.44 g g⁻¹) was reached in media made up of ion-exchange treated hydrolyzates and a commercial glucose solution in proportion 85/15 w/w. Copyright © 2011 Society of Chemical Industry

Colloidal gas aphrons (CGAs), first described by Felix Sebba in his book Foams and Biliquid Foams—Aphrons in 1987, consist of a system of spherical microbubbles with diameters mostly above 25 µm and classified as kugelschaums (ball foam). They possess some colloidal properties and can be pumped at uniform rate through pipes and channels, much like liquids. Also, they have high stability due to very small size and thick surfactant shells. Research work published over the past two decades indicate effective applications of CGAs for clarification of particles and microorganisms, protein separation, gas and nutrient transfer and pollutant separation from water and soil matrices. In this review paper, the techniques for generating CGAs and their application to pollution abatement are discussed. Some mineral separation processes by CGA flotation have also been reviewed because of their relevance to contaminant removal processes. The CGAs were found to function on the principles of bubble entrained floc flotation, electrostatic and ionic interaction, diffusion of entrapped gas and hydrophobicity of the pollutant particles. Two tables have also been provided to present a comparative overview of the generation technologies and the effectiveness of pollution remediation techniques. Copyright © 2012 Society of Chemical Industry

BACKGROUND: The poly(3-hydroxybutyrate)—P(3HB)—is a polyester synthesized by many bacteria and stored as an energy reserve material in the cell cytoplasm as water-insoluble inclusions. The aim of this research was to present a mathematical modeling approach in order to describe the culture kinetics of the bacterium Bacillus megaterium for the production of poly(3-hydroxybutyrate).

RESULTS: Four different models were proposed, differing in the expressions used for specific growth and polymer production rates. The predictions of these models were compared with experimental data and against the results of other models reported in the literature.

CONCLUSION: Analysis of the experimental data under controlled and uncontrolled pH conditions showed that the inclusion of a correction factor for products formation, as well as a term related to the influence of H⁺ cations, are important for the correct modeling of this bioprocess. Compared with earlier models reported in the literature the proposed models show better fitting, with less or equal numbers of parameters, and provide parameter estimates with much lower variability. Copyright © 2011 Society of Chemical Industry

BACKGROUND: Butanol fermentation is product limiting owing to butanol toxicity to microbial cells. Butanol (boiling point: 118 °C) boils at a higher temperature than water (boiling point: 100 °C) and application of vacuum technology to integrated acetone–butanol–ethanol (ABE) fermentation and recovery may have been ignored because of direct comparison of boiling points of water and butanol. This research investigated simultaneous ABE fermentation using Clostridium beijerinckii 8052 and in situ butanol recovery by vacuum. To facilitate ABE mass transfer and recovery at fermentation temperature, batch fermentation was conducted in triplicate at 35 °C in a 14 L bioreactor connected in series with a condensation system and vacuum pump.

RESULTS: Concentration of ABE in the recovered stream was greater than that in the fermentation broth (from 15.7 g L⁻¹ up to 33 g L⁻¹). Integration of the vacuum with the bioreactor resulted in enhanced ABE productivity by 100% and complete utilization of glucose as opposed to a significant amount of residual glucose in the control batch fermentation.

CONCLUSION: This research demonstrated that vacuum fermentation technology can be used for in situ butanol recovery during ABE fermentation and that C. beijerinckii 8052 can tolerate vacuum conditions, with no negative effect on cell growth and ABE production. Copyright © 2011 Society of Chemical Industry

BACKGROUND: 2,2′-disbenzothiazole disulfide is widely used as a vulcanization accelerator in rubber production and as an intermediate in the drug industry. Its current industrial process, the oxidation of 2-mercaptobenzothiazole by sodium nitrite in acidic solution, produces large quantities of liquid waste water. A novel and green synthetic method was developed, which used dioxygen as the oxidant and 2,2,6,6-tetramethylpiperidyl-1-oxyl (TEMPO) as the catalyst without any metallic compounds.

RESULTS: The conditions, including temperature, solvents, amount of catalyst, dioxygen pressure and time, were optimized. Thus 94% yield of 2,2′-disbenzothiazole disulfide was obtained at 60 °C in acetonitrile under 0.2 MPa oxygen pressure for 3 h. Theoretical calculations and UV spectra showed that hydrogen-transfer reaction between 2-mercaptobenzothiazole and TEMPO was the key step, and 2,2′-disbenzothiazole disulfide was generated by the coupling of the formed thiyl radical of 2-mercaptobenzothiazole.

CONCLUSION: 2,2′-disbenzothiazole disulfide was prepared efficiently by aerobic oxidative coupling of 2-mercaptobenzothiazole with TEMPO as the catalyst. This ‘environmentally friendly’ approach with easy handling, mild reaction conditions and simple separation represents a viable means of producing 2,2′-disbenzothiazole disulfide. Copyright © 2011 Society of Chemical Industry

BACKGROUND: R-mandelic acid is an important chiral pharmaceutical intermediate, which is commonly obtained by biotransformation. This work has focused on using novel chiral recognition technology, aqueous two-phase extraction, for the chiral separation of mandelic acid.

RESULTS: The copper (II) formed a 2:1 complex with β-CD in an alkaline solution, which was isolated from solution by the addition of ethanol. The complex structure was characterized by IR and UV spectroscopy. The chiral recognition system was established by adding Cu₂-β-CD into the triton-114 aqueous two-phase extraction system, which preferentially recognizes the (R)-enantiomer rather than the (S)-enantiomer. Factors affecting the extraction mechanism were analyzed, namely the concentration of Cu₂-β-CD and tritonX-114, the types of salts, pH, and temperature. It was found that the concentration of Cu₂-β-CD and temperature were the most important influencing factors for chiral separation of mandedlic acid. The experimental results showed that the ee values increased with pH and concentration of trition-114, and the maximum ee was 67.91%. The addition of inorganic salt had a strong influence on ee, which decreased when salt was added into the aqueous two-phase extraction system.

CONCLUSION: A novel chiral recognition technology - aqueous two phase extraction is reported in this paper.The tritonX-114 aqueous two phase system have a good recognition ability for mandelic acid. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Six different wine yeast strains (G1, X4, X5, P29, QA23, Uvaferm BC) were co-immobilized in a natural, spontaneous way with Penicillium chrysogenum under special conditions without the need for an external support or chemical binder and provided six different ‘yeast biocapsules’. The purpose was to characterize and evaluate the biocapsules obtained in terms of yeast cell viability, ethanol production and reusability to assess their suitability for ethanol production and the development of industrially competitive alternative wine and beer production methods.

RESULTS: Biocapsule size was found to decrease and quantity to increase with increasing shaking rate during the immobilization process. The fermentations were realized in YPD medium containing 18% (w/v) glucose with repeated fermentations reaching 10% (v/v) ethanol. X4 and Uvaferm BC biocapsules afforded at least seven uses with no significant decrease in ethanol production; P29 and QA23 biocapsules five times; and G1 and X5 three times each. Seemingly, ethanol production was directly related to the viability of yeast cells in the immobilizate under defined assay conditions.

CONCLUSIONS: X4 and Uvaferm BC may be the most suitable yeast strains for autoimmobilization on P. chrysogenum with a view to their use in alcoholic fermentation processes. Copyright © 2011 Society of Chemical Industry

BACKGROUND: Cellular foam materials are a new type of catalyst support that provides improved mass and heat transport characteristics and similar pressure drops to other well-established structured supports such as monoliths.

RESULTS: A Pd-based catalyst has been prepared using a moderate surface area (25 m² g⁻¹) β-SiC foam support without further washcoating. The stability of this catalyst has been tested for methane combustion at lean conditions, showing a small decrease of activity during the first 10 h followed by stable performance. Characterization of fresh and aged catalyst shows no significant changes. The influence of the most important reaction conditions, such as reactor loading (0.25–1 g), temperature (300–550 °C) and inlet methane concentration (833 and 1724 ppm), was studied in a fixed-bed reactor. The results were fitted to three kinetic models: Mars-van Krevelen; Langmuir-Hinselwood; power-law kinetics.

CONCLUSIONS: The Pd/β-SiC foam catalyst, prepared without the previous addition of a washcoating has been demonstrated to be stable for the combustion of methane-air lean mixtures. A Mars-van Krevelen kinetic model provides the best fit to the results obtained. Copyright © 2011 Society of Chemical Industry

BACKGROUND: Rhamnolipids biosurfactants mainly produced by Pseudomonas aeruginosa have a wide range of potential applications. However, production of rhamnolipids on a large scale is constrained by severe foaming in fermentation. This study addressed the applicability of organic solvents as both defoamer and carbon substrate in rhamnolipids fermentation.

RESULTS: In this work, although isopropanol and n-butanol performed better defoaming activities against rhamnolipid-induced foams, ethanol was focused on as a potential defoamer due to its high bioavailability and low toxicity in a shaking culture of P. aeruginosa ZJU. The most appropriate dose of ethanol addition was determined to be 1% (v/v) and the best time for addition was after 48 h of culture in shaking flasks. The capability of ethanol to control foaming was further illustrated during rhamnolipids fermentation in 2 L and 50 L bioreactors. In both fermentations, the addition of ethanol not only suppressed severe foaming but also supported cell growth.

CONCLUSIONS: The use of ethanol as a defoamer is a potential strategy to avoid undesirable foam in fermentation of biosurfactant. Copyright © 2012 Society of Chemical Industry

BACKGROUND: Microbial behavior in batch reactors may be different from that in continuous flow reactors, which is expected to affect microbial response to heavy metal exposure. Four parallel continuous flow reactors and batch growth tests were used to investigate the single and joint toxicity of Zn and Cu to Artrobacter sp. JM018.

RESULTS: The results indicated that Cu is more toxic than Zn under all conditions. In the batch reactors, all Zn concentrations showed a stimulatory effect on microbial growth. However in the continuous system, 125 µmol L⁻¹ Zn exposure produced inhibition. In the case of mixed Zn and Cu exposures in the batch system, the presence of Zn reduced the severity of Cu inhibition, with a net impact of reduced growth in all cases, whereas in the continuous system microbial growth and substrate utilization rates sharply decreased and ceased.

CONCLUSION: The results clearly showed that growth in batch reactors underestimated significantly the heavy metal inhibition, compared with the continuous system. Therefore, the results of batch reactor tests should not be used directly when heavy metal inhibition is to be interpreted for continuous flow systems. Copyright © 2011 Society of Chemical Industry

BACKGROUND: Veratric acid (VA, 3,4-dimethoxy-benzoic acid) is representative of the polyphenolic type compounds present in olive mill wastewater (OMW). Given the bactericide factor, the inhibitor character and the anti bacteriological activity of this compound, traditional biological digestion cannot be applied and therefore new technologies, such as electrochemical oxidation using a boron-doped diamond (BDD) anode have to be considered to avoid its accumulation in the environment.

RESULTS: The electrochemical oxidation of aqueous solutions containing 1 mmol L⁻¹ VA has been investigated using a filter-press reactor with a BDD anode during galvanostatic electrolysis. The influence of several operating parameters, such as applied current density, temperature, flow-rate and supporting electrolyte concentration and type has been investigated. The experimental results showed that under the experimental conditions used the oxidation of VA was under mass-transfer control and VA was completely degraded by the reaction with hydroxyl radicals electrogenerated at the BDD surface. The chemical oxygen demand (COD) decay kinetic followed a pseudo-first-order reaction and the apparent rate constant increased with flow rate and temperature. Under optimal experimental conditions of flow-rate (300 L h⁻¹), temperature (35 °C) and current density (10 mA cm⁻²), 99.5% of COD was removed during 2 h electrolysis, with 16.4 kWh m⁻³ energy consumption.

CONCLUSIONS: This study suggests that anodic oxidation with a BDD electrode is an excellent method for the treatment of effluents contaminated with VA and related polyphenols. Copyright © 2011 Society of Chemical Industry

BACKGROUND: Xylitol, a sugar alcohol widely used in food and pharmaceutical industries, can be produced through biological reduction of xylose present in hemicellulose hydrolysates by Candida tropicalis. However, the aeration rate and by-products originating from hemicellulose hydrolysis strongly inhibit the production of xylitol in a fermentation process. A two-stage fed-batch fermentation system was developed to reduce these inhibitory effects and to improve xylitol production from corn cob hemicellulose hydrolysates by C. tropicalis.

RESULTS: Results of batch fermentations indicated that high xylitol production could be obtained from C. tropicalis at an initial xylose concentration of 80 g L⁻¹ in corn cob hydrolysate medium at an aeration rate of 0.4 vvm at the micro-aeration stage. In the two-stage fed-batch fermentation process, 96.5 g L⁻¹ xylitol was obtained after 120 h, giving a yield of 0.83 g g⁻¹ and a productivity of 1.01 g L⁻¹ h⁻¹, which were 12.16% and 65.57% higher than those in a batch fermentation.

CONCLUSION: High xylitol production can be achieved in a two-stage fed-batch fermentation process, in which the negative effects of aeration rate and inhibitory compounds on xylitol formation can be considerably reduced. Copyright © 2011 Society of Chemical Industry

BACKGROUND: This research provides a new approach to the effective use of microalgal biomass waste generated by biofuel conversion processes. In this study, a novel adsorbent for Au(III) recovery was prepared by treating microalgal residues with concentrated sulfuric acid.

RESULTS: The prepared adsorbent, crosslinked microalgae, exhibited high affinity and selectivity for Au(III) over other precious and base metal ions in a hydrochloric acid medium. From the adsorption isotherms, the maximum adsorption capacity of the crosslinked microalgae for Au(III) was estimated to be 3.25 mol kg⁻¹ (640 g kg⁻¹), which was about eight times higher than the adsorption capacity of the microalgal residue. Microphotographs, scanning electron microscopy, and X-ray diffraction confirmed the formation of metallic Au, suggesting that a redox reaction had taken place between the adsorbent and Au(III) ions during adsorption. Comparison of Fourier-transform infrared spectra before and after adsorption indicated that hydroxyl groups as well as ether oxygen atoms in the crosslinked microalgae participated in the Au(III) uptake mechanism. It also suggested that the reduction of Au(III) to Au(0) was facilitated by hydroxyl groups in the crosslinked microalgae.

CONCLUSION: The results presented in this paper are very promising for the practical use of microalgal residues for the recovery of Au(III) because of good selectivity and favorable adsorption capacity for Au(III). Copyright © 2011 Society of Chemical Industry

BACKGROUND: Because of the lower fluidization energy required and the protection against shock loading and starvation due to their sorption capacity, light adsorbents such as hydrogels could be used as biofilm carrier media in fluidized bed bioreactors for wastewater processing. This work explores the feasibility of a cyclodextrin hydrogel as biomass support to degrade phenol under extremely low-nitrogen availability and under nitrogen amendments.

RESULTS: Phenol removal capacity was low (mean 0.589 kg m⁻³ day⁻¹) under extreme nitrogen-limited conditions (mean C:N ratio 3830). A pulsed nitrogen amendment increased the elimination capacity (up to 1.97 kg m⁻³ day⁻¹) controlling the biofilm thickness. An 8-h nitrogen pulse had a highly efficient long-term effect removing 93.5 mg-C mg⁻¹-N in 300 h. The continuous nitrogen amendment enhanced the elimination capacity (up to 5.84 kg m⁻³ day⁻¹) although rapidly increasing the biomass growth. The inhibiting phenol concentration was smaller during the nitrogen-limited period (below 100 mg L⁻¹) than in the nitrogen-amendment periods (140 mg L⁻¹). Low liquid velocities were needed to fluidize the bioparticles (less than 3.1 mm s⁻¹) during the entire experimentation.

CONCLUSION: This work shows that a fluidized-bed bioreactor with mixed culture on cyclodextrin-based particles can be operated for long periods at extreme nitrogen limitation, and that a limited nitrogen supply with periodic pulsed amendments would be adequate for controlling the biofilm thickness. Copyright © 2011 Society of Chemical Industry

BACKGROUND: Shortcut biological nitrogen removal (SBNR) has attracted much attention in recent years due to lower aeration and chemical oxygen demand (COD) requirements, shorter residence time and smaller biomass production. In this work an oil reservoir denitrifying culture, with the ability to function under autotrophic and heterotrophic conditions was used for heterotrophic denitritation. Using freely suspended cells, effects of nitrite concentration (10–50 mmol L⁻¹) and temperature (15–35 °C) on the kinetics of denitritation were investigated and a kinetic model was developed. Potential for enhancement of nitrite removal rate, and impacts of nitrite concentration and loading rate were investigated in a continuous biofilm reactor.

RESULTS: Nitrite did not impose any inhibitory effect, even at the highest applied concentration of 50 mmol L⁻¹. Increase of temperature in the range 15–35 °C enhanced the reduction rate significantly. Fitting the experimental data into the model developed, values of biokinetic coefficients (µ_max−NO2, K_S−NO2, Y_X−NO2, Y_{X−Ace−NO2} and Eµ-_NO2) were determined. In the biofilm reactor increases in nitrite loading rate (through flow rate or feed nitrite concentration) led to a linear increase of nitrite removal rate, with the highest removal rate of 140.6 mmol L⁻¹ h⁻¹ achieved with a residence time of 0.19 h.

CONCLUSION: The enrichment culture used in this study is not only a superior biocatalyst for simultaneous removal of sulphide, nitrate and BOD, it could also be used effectively in the denitritation step of an SBNR process. The kinetic model developed would certainly have beneficial applications in the design, operation and control of the SBNR process. Copyright © 2011 Society of Chemical Industry

BACKGROUND: Sal (Shorea robusta) deoiled seed cake extract (SDOCE) was assessed for its suitability as a cheap natural substrate for lipase production under submerged fermentation. The bacterial isolate Aeromonas sp. S1 isolated from dairy industry was used for lipase production. Both the isolate and its lipase were shown to be potential tools for treatment of dairy wastewater containing higher organic load.

RESULTS: On substituting tributyrin with SDOCE, lipase production was enhanced 24-fold (195 U mL⁻¹) compared with the initial 8.13 U mL⁻¹ lipase activity. Maximum lipase production was obtained at pH 8.0 and incubation temperature 30 °C. The lipase had pH and temperature optima of 10.0 and 55 °C, respectively. The isolate and its crude enzyme preparation were checked separately for applicability in dairy wastewater treatment. The isolate was able to reduce chemical oxygen demand (COD) by 93%, oil and grease (O&G) by 75%, and total suspended solids (TSS) by 47% after 96 h of treatment. Enzymatic preparation gave 86% reduction of COD after 12 h and 75 and 45% reduction of O&G and TSS, respectively, after 96 h of treatment.

CONCLUSION: Overall, the study shows the usefulness of Sal seed deoiled cake, a cheap agro-industrial by-product for the production of lipase. The isolate and its lipase can also be used effectively for the treatment of dairy wastewater. Copyright © 2011 Society of Chemical Industry

BACKGROUND: Solid surfaces possessing both superhydrophobic and superoleophilic properties have attracted great interest for fundamental research and potential application. However, fabrication of the reported surfaces is usually time-consuming and the wetability of the surfaces could not be achieved to the desired level in rugged environments.

RESULTS: A hierarchical stainless steel mesh film comprising structures with three scales of roughness was synthesized by a simple chemical bath deposition method. After being modified with a low surface energy material e.g. Teflon, these films exhibit superhydrophobic and superoleophilic properties. In this study it was demonstrated that the unique properties of the as-prepared films match well with the requirements for the effective separation of oil and water mixtures.

CONCLUSION: It was confirmed that the unique surface wetability of the surface is due to the cooperative effect of the hierarchical structures of the stainless steel mesh films and the natural low surface tension of Teflon. Furthermore, fabrication is simple and economic, and the surface exhibited robust durability even in a rugged environment. Copyright © 2011 Society of Chemical Industry

BACKGROUND: Bacterial cellulose (BC) synthesized by Acetobacter xylinum has been shown to be a potential matrix for impregnating carbon nanotubes (CNTs) to produce bacterial cellulose/carbon nanotubes (BC/CNTs) nanocomposite. The objective of this study was to investigate the crystal structure of BC/CNTs nanocomposite after acetylation treatment. Approximately 0.05 w/v% CNTs were added onto continuously developed BC. Then, the BC/CNTs nanocomposite was acetylated heterogeneously.

RESULTS: The crystallinity characteristic of formed BC/CNTs acetate was analyzed using an X-ray diffractometer (XRD). The crystallization index (CrI) of BC/CNTs acetate was better than BC acetate, i.e. 97:3 and 93:7, respectively. The crystallite size of BC microfibrils in BC/CNTs sheet was reduced because of the impregnated CNTs. However, the reduction of crystallite size for BC/CNTs acetate was lower than that of BC acetate showing that the existence of CNTs within BC micofibrils had protected the BC crystal structure from further destruction by acetylating agent.

CONCLUSION: CNTs is a powerful substance that acted as a void filler between BC crystalline structure and protected the nano-biocomposite from total degradation by the acetylation process. Copyright © 2011 Society of Chemical Industry

BACKGROUND: Effluent released from industry is a mixture of various pollutants. For the degradation of complex pollutants, mixed bacterial cultures can be more effective than a single culture. This study investigated the balance of bacterial populations in a mixed culture for maximum reduction of pollutants.

RESULTS: This study deals with the degradation and detoxification of pulp paper mill effluent (PPME) by three bacterial strains, i.e. Serratia marcescens, Serratia liquefaciens and Bacillus cereus in different ratios, and found that two ratios, 4:1:1 and 1:4:1, were effective for the degradation of PPME. These ratios reduced the various pollution parameters. Enzyme bioassay revealed that more enzyme was produced during degradation for the ratio 4:1:1. High performance liquid chromatography (HPLC) analysis showed that the ratio 4:1:1 degraded 95% of lignin and related compounds, and chlorophenols up to 98%, whereas ratio 1:4:1 reduced lignin by 84% and chlorophenols by 58% after 7 days incubation. Degradation products were confirmed by gas chromatography–mass spectrometry (GC-MS) analysis. A seed germination bioassay on Phaseolous mungo L. revealed that toxicity was reduced by the ratio 4:1:1.

CONCLUSION: Due to variable potential of different bacteria show variation in their growth pattern at any contaminated site. This study shows that an appropriate ratio of mixed cultures is required for maximum degradation and detoxification of PPME. Copyright © 2012 Society of Chemical Industry