Biochemical Mechanism Of Fermentative Hydrogen Production By Bacteria

The three fermentation types are discussed in fermentative hydrogen production by mixed culture. Butyric acid-type and ethanol-type are main hydrogen production pathways in mixed culture system. The optimum liquid phase terminal fermentation product of acid-producing phase is the same with that of organism hydrogen-producing, so one of acetic acid and ethanol and butyric acid can be used as the optimum liquid phase terminal fermentation product. Fermentation bacteria lack electron transfer system, and therefore redundant electrons formed through dehydrogenation in fermentation must be removed through other routes. NADH/NAD(+) is often used as a media inside organism. Fermentation process is controlled by NADH+H(+) negative feedback and NADH/NAD(+) equilibrium adjustment is one of the keys to control fermentation product. There are two routes for fermentative hydrogen evolution. Firstly, direct H(2)-producing route is in biochemical reaction. Secondly, NADH/NAD(+) equilibrium adjustment produces H(2). The utilization of H(2) by homo-type acetic acid-producing bacteria is thought as interspecies hydrogen transfer.