Behavior of acidogenesis during biohydrogen production with formate and glucose as carbon source: Substrate associated dehydrogenase expression

• Acidogenic activity of mixed culture was studied with formate and glucose.
• H2 production was correlated with statistical and stoichiometric analysis.
• Specific hydrogen yield was higher with formate than glucose.
• Role of dehydrogenases correlated well with bio-electrochemical analysis.

Experiments were designed to enumerate variation in biohydrogen (H2) production pattern with formate and glucose as carbon source under acidogenic mixed microenvironment. High H2 production was observed with glucose (180 ml) when compared to formate (152 ml). The process was validated with modified Gompertz model (R2 = 0.98). Substrate degradation also showed higher removal of glucose (ξCOD, 82%) compared to formate (ξCOD, 53%). Nevertheless, specific H2 yield of formate (6.6 mol H2/kg CODR) obtained was comparatively higher than glucose (5 mol H2/kg CODR). Variation in H2 production was manifested by change in fatty acid composition and substrate degradation pattern. Acetate was obtained as a major metabolic intermediate from the degradation of glucose and a shift in the biochemical pathway towards formation of butyrate occurred after maximum substrate degradation. The role of substrate-dependent dehydrogenase activity was deciphered during H2 production and was evidenced with bio-electrochemical analysis.