Sequential generation of hydrogen and methane from glutamic acid through combined photo-fermentation and methanogenesis

► Glutamic acid was subjected to acidogenic pretreatment to produce metabolites. ► Acidulated solution was treated with zeolite to decrease the NH4+ concentration. ► Pretreated solution was incubated with photosynthetic bacteria to produce H2. ► Residual solution was reused to generate CH4 in sequential methanogenesis. ► H2 and CH4 cogeneration from glutamic acid enhanced energy conversion efficiency.