Physiologic studies with the sulfate-reducing bacterium Desulfovibrio desulfuricans: evaluation for use in a biofuel cell.

The growth kinetics of the sulfate-reducing bacteria Desulfovibrio desulfuricans Essex 6 was investigated under various conditions for potential use in a microbial fuel cell that recovers electrons generated from the reduction of sulfate to hydrogen sulfide. Hydrogen sulfide was found to inhibit growth and decrease both the growth yields and the sulfate-specific reduction rate. Hydrogen sulfide inhibition was direct, reversible, and not due to limitation by iron deficiency. A high initial lactate concentration also retarded bacterial growth, reduced the specific sulfate reduction rates, and gave variable biomass growth yields. This effect resulted from a bottleneck in the lactate oxidation pathway which induced the production of the secondary product butanol. The use of pyruvate as a carbon source was more advantageous than lactate in terms of growth rate and biomass growth yields, with only a slight decrease in the rate of specific sulfate reduction. For equal biomass, a slightly higher current density was generated from lactate than pyruvate, but pyruvate required nearly 40% less sulfate.