Integrated dark- and photo-fermentation: Recent advances and provisions for improvement

Abstract Biohydrogen production from waste materials has been recognized as the promising step towards bioremediation and green energy generation. A large number of microorganisms and diverse range of waste materials have been widely studied for H 2 production. However, H 2 production efficiencies vary depending upon the type of organism, type and composition of waste, physiological conditions, and the reactor used. Some research groups suggest integrated dark- and photo-fermentation processes for optimum utilization of the substrate and higher H 2 yield per mol of substrate. Integration of these two processes increases the H 2 yield, and seems suitable for commercial H 2 production. Review and evaluation of the published data suggest that integrated system holds greater promise for commercial H 2 production. The present review deals with the possibilities of enhancing H 2 yield by integrating dark- and photo-fermentation for commercial use.