Effects of pH and ORP on microbial ecology and kinetics for hydrogen production in continuously dark fermentation

► We studied the effects of pH and ORP on hydrogen producing strains in CSTRs. ► Detailed information of the hydrogen-producing strains was obtained using FISH. ► The variations of ethanol-type and butyric acid-type microbial communities were highlighted. ► We certified the metabolic characteristics using Monod model. ► The specific hydrogen production rate, cellular synthesis rate and energy utilization were also calculated.