Effect of carbon and nitrogen sources on photo-fermentative H2 production associated with nitrogenase, uptake hydrogenase activity, and PHB accumulation in Rhodobacter sphaeroides KD131

► In an NH4Cl medium, the nitrogenase activity was repressed by the ammonium ion. ► Glutamate as an N source was preferred for rapid phototrophic H2 production. ► H2 evolution was repressed over time by increased ammonium in a glutamate medium. ► In the presence of H2, hydrogenase activity increased regardless of the N sources. ► Acetate as a C source caused a low H2 yield due to PHB accumulation and low pH.