Continuous production of hydrogen from mixed volatile fatty acids with Rhodopseudomonas capsulata

Rhodopseudomonas capsulata can use volatile fatty acids as electron donors for continuous H2 production at the expense of light energy. In this study a mixture of acetate, propionate and butyrate was used as the substrate for continuous H2 production from a photo-bioreactor seeded with R. capsulata. For a mixture of acetate 1.8 g/l, propionate of 0.2 g/l and butyrate of 1.0 g/l, a maximum H2 production rate of 37.8 ml/g dry weight (dwt)/h, a light conversion efficiency of 3.69% and a substrate conversion efficiency of 45% were achieved. Hydrogen was also produced with the effluent from an acidogenic H2-producing reactor at a maximum production rate of 24.9 ml/gdwt/h by R. capsulata. The H2 yield increased by three-fold through combining H2 production of anaerobic fermentative bacteria and R. capsulata, compared with the dark fermentation only.