The effect of redox potential on methanogenesis by thermophilic methanogens

The influence of the redox potential (Eh) of incubation medium on the methanogenesis of resting cultures of the thermophilic methanogenic bacteria Methanosarcina thermophila TS-2 and Methanobacterium thermophilum M was studied. Both cultures produced methane at Eh values from +100 to -400 mV. The values of Eh optimal for methanogenesis were different for these methanogens and depended on the carbon and energy source. With the redox potential of the medium being changed toward negative or positive suboptimal values, the production of methane persisted, although at a slower rate. The ability of methanogens to alter the redox potential of the medium is probably determined by the composition of the redox chains associated with methanogenesis and energy production.