Immobilized purple bacteria for light-driven H2 production from starch and potato fermentation effluents



The goal of the study was to show that immobilized purple bacteria could photoproduce H2 using dark fermentation effluent (FE) as substrate. Simple pretreatment of an inexpensive glass–fiber matrix accelerated the immobilization process. Photobioreactors (PhBR) containing immobilized Rhodobacter sphaeroides GL produced 0.128 L H2 h−1 L−1 of PhBR volume (0.570 L h−1 L−1 of matrix) for up to 3 months when continuously fed artificial media with volatile fatty acids (VFAs) or FE from potato and starch fermentations. Hydrogen production was insensitive to NH4+ up to 1 mM and saturated at 8 mM lactate or 1.5% potato FE (diluted in water and supplemented with critical micronutrients). The efficiency of VFA transformation to H2 was 50–70% of theoretical. At nonlimiting substrate concentrations in artificial media or FE, acetate was utilized before butyrate. High volumetric rates of continuous H2 photoproduction and stability of the process are advantages of using immobilized cultures. Use of H2 photoproduction as a polishing step in the treatment of FEs from dark fermentations increased the total amount of H2 produced from 0.9 to 4.7 mol mol−1 glucose equivalent in the original potato homogenate. © 2011 American Institute of Chemical Engineers Biotechnol. Prog., 2011