Photo fermentative hydrogen production using dominant components (acetate, lactate, and butyrate) in dark fermentation effluents

► Soluble metabolites from dark fermentation were converted to H2 by photo fermentation. ► Kinetics of cell growth and H2 production by R. palustris WP3-5 was identified. ► Integration of dark and photo fermentation led to a high yield of 6 mol H2/mol hexose.