Upgrading biogas allows for the injection of biomethane into the natural gas grid and thus a decentralized use. Since the currently available techniques have a high energy demand, there is a high potential to improve biogas upgrading. Innovative CO2-separation of biogas by the use of polymer resins can reduce the energy demand, the capital expenditure and the operational costs. In this study, we show the ability of polymer resin to selectively adsorb CO2. Desorption tests showed the potential for continuous use of the resin. In a continuous lab-scale plant numerous variations of process parameters were carried out and optimization possibilities were demonstrated. Methane purity up to 98 % was achieved. The favorable estimated energy demand indicates the great potential of the demonstrated improved process.
To improve the effects of protease finishing on wool, 1-butyl-3-methylimidazolium chloride ionic liquid was employed as a pretreatment reagent. It was found that ionic liquid pretreatment significantly changed the wool surface characteristics. The Allwördern reaction showed that the epicuticle layer was damaged by the ionic liquid, and X-ray photoelectron spectroscopy analysis further demonstrated that the surface elemental composition was significantly changed. Ionic liquid pretreatment remarkably improved the accessibility of protease to the wool and thus accelerated the hydrolysis rate of keratin. The properties of wool fabric after combined processing were also changed. Dyeability results showed that the color depth was increased but the wet rubbing and washing fastness of wool fabrics showed a decreased half grade. The wettability results demonstrate that the contact angle was further reduced after the comprehensive treatment because of the exposure of more proteins under the fatty-acid layer. In addition, the shrink proofing of wool fabric was also enhanced after combined processing. In summary, ionic liquid modification presents a promising pretreatment method for protease processing of wool.
Lactic acid bacteria (LAB) play a central role in several food fermentations, producing lactic acid besides other metabolic actions. Popular fermented foods that rely on the use of LAB include fermented meats, sourdoughs, and fermented dairy products. During fermentation, LAB are frequently accompanied by other microorganisms, such as coagulase-negative staphylococci (CNS), yeasts, and filamentous fungi. Whereas fermentation was originally a spontaneous and empiric process, most industrial processes make now use of starter cultures to speed up the fermentation process and standardise the end-products and to reduce the risks on misfermentation. A drawback of using commercial starter cultures is their suboptimal selection, which is often solely based on mere technological features. Currently, functional starter cultures are being developed to further optimise the process and to yield additional nutritional, safety, and quality benefits. Specific metabolic properties are being sought for, with a focus on novel, interesting molecules that may, for instance, inhibit undesirable microorganisms, display nutraceutical properties, or contribute to flavour and texture attributes.
]]>Industrial-scale plant cell-based bioprocesses are limited because of technological challenges associated with mass transfer and mixing in the heterogeneous broth which typically displays non-Newtonian characteristics. Cultures of Centaurea calcitrapa cells, presenting milk-clotting activity, were established in a 7-L stirred-tank reactor (STR), keeping the initial mass transfer conditions constant, to gain a better understanding of the effects of the hydrodynamic environment and mass transfer on protease production. Cell suspensions grown in an STR equipped with one single marine propeller or two Rushton turbines showed the highest protease activities and biomass production, corresponding to the adequate mass transfer achieved under the tested bioreactor conditions. The key factors improving milk-clotting protease production in a bioreactor were an efficient mass transfer and good bulk mixing without the formation of stagnant zones, while a compromise had to be established in relation to the hydrodynamic shear conditions.
]]>The objective of this study was the development and optimization of a probiotic apple beverage as well as the establishment of a sensory profile by using chemical, microbiological and quantitative descriptive analysis (sensory profiling). For this purpose, both Lactobacillus casei and L. acidophilus were tested in two different media - Fuji and Gala apple juices - at different pH values. The optimal conditions to develop the apple probiotic beverage were obtained by response surface methodology. They were found to be 10 hours of fermentation at 37oC in Gala apple juice. Sensorially, the clarified Gala apple juice was characterized by a caramel color, apple aroma, and an acidic apple taste. The fresh fermented probiotic apple beverage was characterized by a thick texture and sweet taste. The probiotic apple beverage stored for 28 days at 7oC presented a thick texture and acidic taste. Finally, when the fermented probiotic beverage was tested by potential consumers, it presented an acceptance index of 96%.
]]>This study investigates the effects of enzymatic treatment with microbial trans-glutaminase (m-TGase) on the physical and mechanical properties of the depigmented wool yarns. Coarse pigmented wool yarns were treated with iron (II) followed by depigmentation with both oxidative and oxidative-reductive chemicals. The depigmented wool yarns were then treated with m-TGase to reduce the negative effects of the harsh chemicals. Diverse features of the wool yarns, including: tensile strength, elongation, color, diameter, moisture content, alkali solubility and weight reduction were measured before and after bleaching and enzymatic treatments. The treatment with the oxidative and reductive agents led to reduced tensile strength and elongation and increased lightness, alkali solubility and moisture content of the yarns. In contrast, the enzymatic treatment by m-TGases cross-linked the proteins of wool fibers via reaction between glutamine and lysine isodipeptide remediated the wool yarns. This improved the tensile strength and elongation and also decreased the alkali solubility and moisture content.
]]>Xylanase production by Aspergillus niger NRRL-567 in solid-state fermentation (koji fermentation) was optimized using 24 factorial design and response surface methodology (RSM). The evaluated variables were the initial moisture level and concentration of inducers [veratryl alcohol (VA), copper sulphate (CS) and lactose (LAC)] concentration, leading to the response of xylanase production. Initial moisture level and lactose were found to be the most significant variable for xylanase production (p < 0.05). The highest xylanase production was observed with 3578.8 ± 65.3 IU/gram dry substrate (gds) under optimal conditions using initial moisture of 85% (v/w), pH 5.0 and inducers VA (2 mM/kg), LAC 2% (w/w) and CS (1.5 mM/kg) after 48 h of incubation time. Higher xylanase activity of 3952 ± 78.3 IU/gds was attained during scale-up of the process in solid-state tray fermentation under optimum conditions after 72 h of incubation time. The present study demonstrates that A. niger NRRL-567 can efficiently be used to achieve xylanase production with an economical and environmental benefit in solid-state tray fermentation. The developed process can be used to develop an effective process for commercially feasible bioproduction of xylanases for speciality applications, such as conversion of lignocellulosic biomass to biofuels and other value added-products.
]]>This study presents and discusses the application of Cy3-labeled aptamers directed against the histidine-tag for the detection of his-tagged proteins on microarrays in a so called reverse phase assay. These types of assays are widely used tools in protein microarray technology. Up to now antibodies are usually applied as detection molecules. Here, two different spotting techniques, contact- and non-contact-spotting, as well as different types of slides, aldehyde-modified glass slides and nitrocellulose membrane-coated slides, were examined and compared. Through this study, we validated the importance of a high protein binding capacity of the microarray, and the labeling position of the fluorophore within the aptamer. Purified his-tagged PFEI (pseudomonas fluorescence esterase I) was thereby used as a model system. Concentrations of PFEI-his as low as 30 nM were detectable. These results demonstrate the applicability of aptamers as stable detection molecules in protein assays. Additionally the reverse phase assay was found to be suitable for the detection of PFEI-his in cell lysates. This might be of further interest in monitoring of protein production and purification processes.
]]>Physical and rheological properties of commercial low-fat yogurt and of skim milk acidified with single strains of S. thermophilus were evaluated. Concentration of exopolysaccharides (EPS) varied from 40 – 168 mg glucose equivalents per litre, and EPS showed different degrees of ropiness. Further characterisation of non-ropy and ropy EPS from three S. thermophilus strains revealed intrinsic viscosity of 0.13 - 0.66 mL/mg, respectively, which had a significant impact on apparent viscosity and the ability of regaining structure after shearing. Compared with regular milk acidification, batch fermentation with supplemented skim milk at constant pH resulted in a strain-dependent increase of EPS yield by a factor of 4 - 7.
]]>So far, time-kill analyses were mostly done with isolates of bacteria. Here, we used a mixed culture consisting of Pseudomonas aeruginosa, Burkholderia cepacia and Staphylococcus aureus to investigate the impact of ceftazidime treatment. Following an earlier study with the same strains, the influence of different ceftazidime concentrations as well as repeated ceftazidime treatment was tested. In order to assess the influence of substrate competition, which might be relevant to interpret mixed-culture time-kill studies, the major metabolites of the chemically defined cultivation medium were measured additionally. Time-kill experiments were conducted in shake flasks with the chemically defined and modified medium M199. The cell concentration in the mixed culture was analysed on the single-species level using a qT-RFLP method. The amount of gluconate produced in mixed culture positively correlated with increased ceftazidime concentrations (5, 15, 30, 60 mg/L). B. cepacia developed resistance after repeated ceftazidime addition and reached the highest cell concentration of the three cultivated strains. P. aeruginosa showed a pronounced regrowth phase after removal of ceftazidime, while growth of S. aureus was not influenced by medium exchange. In conclusion, growth of B. cepacia was dominant in the ceftazidime-treated mixed culture over the observed time range, due to low susceptibility against ceftazidime as well as advantages in substrate usage.
]]>Carbon nanotubes (CNTs) are promising components for electrical biosensors due to their high surface-to-volume ratio and improved electron transfer properties. This review surveys CNT-based label-free indicator-free biosensing strategies that have been demonstrated for the sensitive detection of nucleic acids. After an introduction to CNTs, the fabrication of biosensors and techniques for the immobilization of probe nucleic acids are outlined. Subsequently, two major label-free strategies namely electrochemical transduction and field-effect detection are presented. The focus is on direct detection methods that avoid labels, indicators, intercalating agents, mediators and even secondary receptors. The review concludes with a comparison between the various biosensors and presents ways of engineering them so that they can be deployed in realistic diagnostic applications.
]]>Three alkaline protease producing strains designated as ANFLR1, NPLR1 and PROLR15 were isolated from Labeo rohita fish gut. These strains are able to produce alkaline protease using tannery fleshing (TF) as the sole carbon and nitrogen source and were identified as Bacillus megaterium, Serratia marcescens and novel Pontibacter sps. Proteases from these organisms were purified to electrophoretic homogeneity following ammonium sulphate precipitation, ion exchange and column chromatography. SDS–PAGE revealed molecular weights of the proteases to be 46 kDa (ANFLR1), 52 kDa (NPLR1) and 58 kDa (PROLR15). The optimum pH and temperatures for the protease activity of ANFLR1, NPLR1 and PROLR15 were found to be 10.5, 11.5, 9 and 70°C, 60°C, and 50°C, respectively. The maximum protease activities at the optimum conditions were 420 U/mL (ANFLR1), 550 U/mL (NPLR1) and 530 U/mL (PROLR15). Inhibition of the NPLR1 protease by pepstatin confirmed aspartate type enzymatic activity. Fe3+ enhanced the activity of PROLR15 protease. Unlike all other microbial proteases known so far the PROLR15 enzyme did not require Ca2+ for activity and thermal stability. The SDS-PAGE and SEM analyses confirmed the conversion of high molecular weight substrate (TF) to low molecular weight peptides by these proteases. The alkaline metallo protease production by novel Pontibacter sps and aspartate protease production by Serratia marcescens remains unexplored. Hence, tannery fleshing with its relatively abundant availability can be beneficially utilized for alkaline protease production through the fish gut microbial fermentation processes.
]]>Hydrophobins are small surface-active proteins that have considerable potential for use in applications ranging from medical and technical coatings, separation technologies, biosensors, and personal care. Their wider use would be facilitated by the availability of recombinant tailor-made hydrophobins. We successfully expressed the class II hydrophobin HFB1 from Trichoderma reesei in Pichia pastoris under the control of the constitutive GAP (glyceraldehyde 3-phosphate dehydrogenase) promoter. Avoiding the use of the AOX1 (alcohol oxidase 1) promoter prevents the costs and risks associated with the storage and delivery of methanol used as an inducer. Efficient secretion of hydrophobin was achieved using either the alpha-factor prepro-peptide or the native secretion signal of HFB1. The secreted hydrophobins have been isolated with a purity of up to 70% using in situ foam separation during the cultivation process. Coating experiments and surface pressure measurements demonstrated the activity of the hydrophobins. An immunodot assay showed the accessibility of carboxyterminally fused tags of the hydrophobin, which is necessary for potential applications using functionalized hydrophobins. The presented data show that Pichia pastoris is a suitable system for production of constitutively expressed and secreted active hydrophobin, allowing for in situ pre-purification using foam separation.
The Zymomonas mobilis ZM4 strain with excellent ethanol-producing capabilities was the first strain of Z. mobilis, which was sequenced. This strain is resistant to transformation, and no previous study has shown a detailed protocol for electrotransfer of ZM4 with foreign DNA. In this work, many electrical and biological parameters were selected and evaluated in order to optimize the electrotransformation of ZM4. First, improved transformation efficiencies of 11 896, 99, 96 and 5989 transformants/μg DNA were separately achieved with shuttle plasmid pZB21-mini (3082 bp), pZB21 (5930 bp), pZA22 (6994 bp) and broad-host-range vector pBBR1MCS-2 (5144 bp) all prepared from Escherichia coli JM110. The crucial factors affecting the transformation efficiency included the source of the plasmid (the best strain was ZM4), origin and size of the plasmids, growth phase of the cells (the most ideal phase was early log phase with OD600 of 0.3–0.4), the electric field strength (generally 11.75 kV/cm–13.25 kV/cm) and the recovery time (3–24 h). Further, based upon the optimal transformation protocol mentioned above for replicative plasmids in ZM4, (i) the electrotransformation by recombinant plasmid pBBR1MCS-2-Pgap-FLP (6880 bp) was an immediate success with the transformation efficiency 102 transformants/μg DNA; (ii) the site-specific integration efficiencies (expressed in terms of “per μg of DNA”) of 3–6 integrating transformants was obtained using the integrating plasmid pBR328-ldhR-cml-ldhL (7447 bp). This study will assist genetic and biotechnological research of ZM4 and other Z. mobilis strains by providing information about suitable vectors and a more universal and reliable procedure for introducing DNA into this strain.
An Otto engine CHP-unit running on biogas has been under investigation for more than two years. Within this time data regarding temperatures, energy flows, biogas composition, emissions etc. were collected, and this paper presents some of the results. In detail, electric and thermal output are discussed for one full year. From these data the monthly electric availability of the unit can be calculated, which ranges from 84.0 to 96.4%. In addition, the utilization of the heat produced by the CHP-unit during one year is displayed. It was found that 18.2% of the heat was needed for heating purposes within the biogas plant, and 64.5% of the heat could be supplied to the district heating system. Hence, 17.3% of the useful heat had to be released to the ambient air by an additional cooler. Regarding emissions, a strong impact of the excess air ratio on emissions of NOX has been observed. Moreover, the effect on electric efficiency is outlined in this paper. As known from theory, the experimental results revealed that an increase in the excess air ratio helps to lower NOX-emissions, while electric efficiency is reduced by this means.
To improve biomass and microalgal oil production of Botryococcus braunii, fed-batch culture was investigated in an airlift photobioreactor. The optimal feeding time of the fed-batch culture was after 15 days of cultivation, where 1.82 g/L of the microalgal biomass was obtained in the batch culture. Nitrate nutrient was the restrictive factor for the fed-batch cultivation while phosphate nutrient with high concentration did not affect the microalgal growth. The optimal mole ratio of nitrate to phosphate was 34.7:1, where nitrate concentration reached the initial level and phosphate concentration was one quarter of its initial level. With one feeding, the biomass of B. braunii reached 2.56 g/L after 18 days. Two feedings in 2-day interval enhanced the biomass production up to 2.87 g/L after 19 days of cultivation. The hydrocarbon content in dry biomass of B. braunii kept at high level of 64.3% w/w. Compared with the batch culture, biomass production and hydrocarbon productivity of B. braunii were greatly improved by the strategic fed-batch cultivation.
Basic fibroblast growth factor (FGF-2) is a cytokine that is used to keep embryonic stem cells in an undifferentiated state. The application is however limited because of its high price. In this issue, Thomas Scheper (Hannover, Germany) and collaborators present a fast and efficient process for the production and purification of FGF-2 from recombinant Escherichia coli cultures with reusable membrane adsorbers. After achieving a high expression level of FGF-2 in fed-batch cultivation, a new combination of cation-exchange membrane chromatography and heparin–sepharose-affinity chromatography is employed to purify the protein. In a polishing step using a novel anion-exchange membrane chromatography, endotoxins and DNA are removed. The described process is suitable as a low-cost preparation of bioactive FGF-2 at bench-scale, which can be applied for the production of other cytokines.……………29
Cellulases have numerous industrial applications. For example in the food and beverage industry, these enzymes are used for the extraction of fruit juices, for coffee processing, improving beer filtration and modification of wine aroma. As cellulases hydrolyze cellulosic materials into sugars that can be fermented into bioethanol, it has an increasing relevance for biofuel and bioenergy production. In Malaysia, palm oil mill effluent (POME) is a waste product in palm oil production. It is rich in carbohydrates, proteins, lipids, minerals, cellulose, hemicelluloses and lignin and is a sustainable supply of biomass for cheap cellulase production. In this issue, authors from Nibong Tebal, Malaysia, present a comprehensive review on cellulases, their application and production with a focus on using POME from Malaysia as a substrate.……………7
de los Cobos-Vasconcelos et al., Eng. Life Sci.2012, 12, 39–48.
Industrially produced azo dyes are designed to resist fading and are not easy to degrade. Inexpensive biological treatments present a practical solution for wastewater treatment in the textile industry, because they can degrade potentially harmful compounds. In this issue, Nora Ruiz-Ordaz et al. from Mexico show the biodegradation of the sulfonated azo dyes, Acid Orange 7 (AO7) and Acid Red 88 (AR88), by a bacterial consortium isolated from water and soil samples. An aerobically operated two-stage rectangular packed-bed biofilm reactor (PBR) was constructed and characterized. Eight bacterial strains were isolated from the biofilm attached to the porous support of the PBR. Interestingly, both dyes present the sole carbon and nitrogen sources used by the microbial consortium.……………39
The demand for cellulases has increased tremendously over the last few decades. This is due to its numerous applications in industry and also because it can be used to hydrolyze cellulosic materials into sugars that can be fermented into bioethanol and bio-based products. This does not only open up a big and significant market for cellulases, but also provides another source of biofuel and bioenergy in the future. Nevertheless, the cost of the existing substrates for cellulase fermentation is very high if required for large-scale production. Sustainable supplies and an economically feasible biomass are needed to reduce the cost of cellulase production. Palm oil mill effluent (POME) is rich in carbohydrates, proteins, nitrogenous compounds, lipids, minerals, cellulose, hemicelluloses and lignin. It can be used naturally as a fermentation medium, either for cellulase or other value-added product fermentation. In Malaysia, a large and continually increasing amount of POME is produced every year because of the high global demand for palm oil. Hence, the development of cellulase production from POME is reviewed, covering the POME production, cellulase production and the major challenges together with the future prospects of these processes.
Basic fibroblast growth factor (FGF-2) is a multifunctional cytokine that regulates various cellular processes both in vitro and in vivo. FGF-2 is extensively used in embryonic stem cell cultures since it can maintain the cells in an undifferentiated state. However, the high price of FGF-2 has limited its application in stem cell research. Here we present a fast and efficient process for the purification of FGF-2 from recombinant Escherichia coli cultures using reusable membrane adsorbers. A high expression level of FGF-2 (42 mg/g dry cell) was achieved by fed-batch cultivation of E. coli BL21(DE3). A new combination of cation exchange membrane chromatography and heparin-sepharose affinity chromatography was used for the purification of the protein. A novel anion exchange membrane chromatography was used in the polishing step to remove endotoxins and DNA. In this new process, about 200 mg soluble FGF-2 was yielded from 1.9 L culture broth with a purity of 98%. The purified protein was identified to be endotoxin-free and bioactive. It was successfully tested to keep primate embryonic stem cell and human-induced pluripotent stem cell pluripotent. Our approach, in which a controlled cultivation process is combined with an optimized fast and versatile downstreaming process, is suitable for low-cost preparation of bioactive FGF-2 at bench-scale and may be beneficial to the effective production of other cytokines.
The biodegradation of the sulfonated azo dyes, Acid Orange 7 (AO7) and Acid Red 88 (AR88), by a bacterial consortium isolated from water and soil samples obtained from sites receiving discharges from textile industries, was evaluated. For a better removal of azo dyes and their biodegradation byproducts, an aerobically operated two-stage rectangular packed-bed biofilm reactor (2S-RPBR) was constructed. Because the consortium's metabolic activity is affected by oxygen, the effect of the interstitial air flow rate QGI on 2S-RPBR's zonal values of the oxygen mass transfer coefficient kLa was estimated. In the operational conditions probed in the bioreactor, the kLa values varied from 3 to 60 h−1, which roughly correspond to volumetric oxygen transfer rates, dcL/dt, ranging from 20 to 375 mg O2 L−1h−1. Complete biodegradation of azo dyes was attained at loading rates BV,AZ up to 40 mg L−1d−1. At higher BV,AZ values (80 mg L−1 d−1), dye decolorization and biodegradation of the intermediaries 4-amino-naphthalenesulphonic acid (4-ANS) and 1-amino-2-naphthol (1-A2N) was almost complete. However, a diminution in COD and TOC removal efficiencies was observed in correspondence to the 4-aminobenzenesulfonic acid (4-ABS) accumulation in the bioreactor. Although the oxygen transport rate improved the azo dye mineralization, the results suggest that the removal efficiency of azo dyes was affected by biofilm detachment at relatively high QGI and BV,AZ values. After 225 days of continuous operation of the 2S-RFBR, eight bacterial strains were isolated from the biofilm attached to the porous support. The identified genera were: Arthrobacter, Variovorax, Agrococcus, Sphingomonas, Sphingopyxis, Methylobacterium, Mesorhizobium, and Microbacterium.
A mathematical model for hexanol oxidation catalyzed by NAD+-dependent alcohol dehydrogenase from baker's yeast in a microreactor was developed and compared with the model when the reaction takes place in a macroscopic reactor. The enzyme kinetics was modeled as a pseudo-homogeneous process with the double substrate Michaelis–Menten rate expression. In comparison with the kinetic parameters estimated in the cuvette, a 30-fold higher maximum reaction rate and a relatively small change in the saturation constants are observed for the kinetic parameters estimated in the continuously operated tubular microreactor (Vm1=197.275 U/mg, Kmhexanol=9.420 mmol/L, and Km1NAD+=0.187 mmol/L). Kinetic measurements performed in the microreactor, estimated from the initial reaction rate experiments at the residence time of 36 s, showed no product inhibition, which could be explained by hydrodynamic effects and the continuous removal of inhibiting products. The Fourier amplitude sensitivity test method was applied for global kinetic parameter analysis, which shows a significant increase in the sensitivity of Km1NAD+ in the microreactor. Independent experiments performed in the microreactor were used to validate and to verify the developed mathematical model.
The ability of bacterial strains to assimilate glycerol derived from biodiesel facilities to produce metabolic compounds of importance for the food, textile and chemical industry, such as 1,3-propanediol (PD), 2,3-butanediol (BD) and ethanol (EtOH), was assessed. The screening of 84 bacterial strains was performed using glycerol as carbon source. After initial trials, 12 strains were identified capable of consuming raw glycerol under anaerobic conditions, whereas 5 strains consumed glycerol under aerobiosis. A plethora of metabolic compounds was synthesized; in anaerobic batch-bioreactor cultures PD in quantities up to 11.3 g/L was produced by Clostridium butyricum NRRL B-23495, while the respective value was 10.1 g/L for a newly isolated Citrobacter freundii. Adaptation of Cl. butyricum at higher initial glycerol concentration resulted in a PDmax concentration of ∼32 g/L. BD was produced by a new Enterobacter aerogenes isolate in shake-flask experiments, under fully aerobic conditions, with a maximum concentration of ∼22 g/L which was achieved at an initial glycerol quantity of 55 g/L. A new Klebsiella oxytoca isolate converted waste glycerol into mixtures of PD, BD and EtOH at various ratios. Finally, another new C. freundii isolate converted waste glycerol into EtOH in anaerobic batch-bioreactor cultures with constant pH, achieving a final EtOH concentration of 14.5 g/L, a conversion yield of 0.45 g/g and a volumetric productivity of ∼0.7 g/L/h. As a conclusion, the current study confirmed the utilization of biodiesel-derived raw glycerol as an appropriate substrate for the production of PD, BD and EtOH by several newly isolated bacterial strains under different experimental conditions.
For screening and isolation of microorganisms harboring nitrile-hydrolyzing enzymes that mediate the hydrolysis of iminodiacetonitrile (IDAN) to iminodiacetic acid (IDA), a sensitive and specific high-throughput screening model was established. This model integrated a solid screen-selective culture medium plate with bromcresol purple as the pH indicator coupled to Cu-IDA complex spectrophotometry. Four strains were selected to perform the biotransformation to IDA, which were isolated and identified as Alcaligenes faecalis, Pseudomonas chlororaphis, Pseudomonas putida and Klebsiella pneumoniae, on the basis of 16S rDNA sequence analysis in combination with physiological and biochemical characterization. Moreover, the maximum specific enzyme activity was 73.4 U/g dry cell weight obtained by A. faecalis ZJUTBX11 after optimization of the medium conditions for enzyme production. The results show that the proposed model is a suitable method for screening microorganisms with nitrile-hydrolyzing enzymes. We suggest the A. faecalis ZJUTBX11 strain to be used for large-scale bioconversion of IDAN to IDA, because of its excellent performance in the production of IDA.
Microalgal biomass produced in indoor photobioreactors can be used as inoculum for large-scale outdoor cultures or directly for the production of high-value bioproducts due to the higher control of these cultures compared with outdoor systems. One of the main costs of indoor microalgal cultures is the illumination. This work can be used as a basis for the optimization of the light source for indoor microalgal biomass production, based on the light source type, irradiance, productivity, growth rate, attenuation coefficients, and contaminant growth on the reactor's side-walls. Four commercially available near 400-W artificial light sources for microalgal cultures (metal halide (MH), high-pressure sodium (HPS), Son Agro®, and fluorescent) were compared. The light elevation and the surface scalar irradiance were shown to have a linear relationship. The attenuation coefficient in air (ka) was highest with Son Agro®. A linear partition of the attenuation coefficient between the water and biomass and an exponential relationship between average scalar irradiance and depth were found. An empirical overall scalar attenuation coefficient for each light source was obtained. The lowest maximum observed growth rate was obtained with fluorescent light (0.98 d−1) and the highest with Son Agro® (2.39 d−1). The highest growth on the reactor's wall was obtained with Son Agro®. Further studies resulted in a higher maximum specific growth rate and optimum irradiance for HPS (2.37 d−1 and 460 μmol s−1 m−2) compared with those observed with MH (1.73 d−1 and 391 μmol s−1 m−2).
Recently, it had been shown that Euglena gracilis was able to grow heterotrophically not only on synthetic media, but also on media based on potato liquor. Supplementation with glucose in both cases led to the accumulation of paramylon, a β-1,3-glucan. Thus, such a process may yield a valuable product accompanied by the revaluation of an otherwise annoying waste stream of the potato-starch industry. Actually, process strategies have been evaluated in order to optimise the concentration of paramylon obtained at the end of the cultivation process. Therefore, cultivation processes based on fed-batch and in particular repeated-batch strategies have been studied. It is shown that repeated-batch operation maybe particularly suited for such a process since E. gracilis seems to adapt gradually to the cultivation medium so that the concentration of media components may be increased step by step. Repeated-batch cultivation of E. gracilis leads to biomass concentrations in access of 20 g/L with a consistent paramylon mass fraction of about 75%. Cultivations have been carried out at an operating temperature of 27.5°C. As had been found earlier already, pH control is not required during cultivation. On the basis of these results it is clear that repeated-batch cultivation represent a simple and economic way for the production of paramylon by heterotrophic cultivation of E. gracilis.
Two brown algae, Macrocystis pyrifera and Undaria pinnatifida, were employed to remove Cr(III) from aqueous solutions. Both seaweeds were characterized in terms of alginate yields. The alginate contents were 20 and 30% of the dry weight for M. pyrifera and U. pinnatifida, respectively. Kinetics experiments were carried out at different initial pH values. Cr(III) biosorption was affected by the solution pH. The highest metal uptake was found at pH 4 for both biosorbents. Different models were applied to elucidate the rate-controlling mechanism: pseudo-first-order, pseudo-second-order, external mass transfer and intra-particle diffusion. The application of Langmuir, Freundlich and Dubinin–Radushkevich models to the equilibrium data showed a better fitting to the first model. The maximum Cr(III) sorption capacity (qm) and the affinity coefficient (b) were very similar for both biosorbents: 0.77 mmol/g and 1.20 L/mmol for M. pyrifera and 0.74 mmol/g and 1.06 L/mmol for U. pinnatifida. The free energy of the sorption process was estimated using the Dubinin–Radushkevich isotherm. The values indicate that the processes are chemical sorptions. To evaluate the significance of the ion-exchange mechanism, the light metals (Ca2+, Na+, Mg2+ and K+) and pH were measured during the experiments.
A recent article of Zavrel et al. in this journal (Eng. Life Sci. 2010, 10, 191–200) described a comparison of several computer programs for progress-curve analysis with respect to different computational approaches for parameter estimation. The authors applied both algebraic and dynamic parameter estimations, although they omitted time-course analysis through the integrated rate equation. Recently, it was demonstrated that progress-curve analysis through the integrated rate equation can be considered a simple and useful alternative for enzymes that obey the generalized Michaelis–Menten reaction mechanism. To complete this gap, the time-dependent solution of the generalized Michaelis–Menten equation is here fitted to the progress curves from the Zavrel et al. reference article. This alternative rate-integration approach for determining the kinetics parameters of Michaelis–Menten-type enzymes yields the values with the greatest accuracy, as compared with the results obtained by other (algebraic or dynamic) parameter estimations.
The knowledge of thermal inactivation kinetics, usually expressed in terms of D- and z-values, is of crucial importance for the design of sanitation and sterilization processes. In this study, we designed a simple, fast-responding, and mechanically stable aluminum tube for inactivation measurements and compared these experiments with the successive-sampling method at different temperatures. Up to 65°C, we determined a come-up time of approximately 15 s for the tubes, which is lower than the corresponding values of other devices, presumably because of lower wall thickness, material properties, and a higher surface to volume ratio. D-values of Escherichia coli calculated from tube inactivation experiments by first-order kinetics were 370 s (56°C), 126 s (58°C), 53.2 s (60°C), 33.8 s (62°C), and 3.22 s (65°C), and the corresponding values determined with the successive-sampling flask method were insignificantly different (417, 138, 48.6, and 29.1 s for 56, 58, 60, and 62°C, respectively). These data as well as those measured for Enterobacter cloacae, Pseudomonas putida, Serratia odorifera, and Yersinia rhodei were in close accordance with literature values.
Successful surfactant removal from wastewater is often limited by the high concentration of the surfactant. The use of advanced oxidation processes can be the key to aid biological treatment of water containing high amounts of surfactants. The present study analyzes the biodegradation of the anionic surfactant sodium dodecylbenzenesulfonate (SDBS) and the effects of its combination with ozonation. SDBS pre-ozonation favors the metabolism by microorganisms. Experimental results indicate that the application of a concentration of up to 60 μM of ozone for 60 min, prior to contact with microorganisms, increases the percentage of SDBS removed by biodegradation alone. These results demonstrate that the removal of SDBS and of the total organic carbon is increased by the consecutive use of ozonation and biodegradation.