PHYSIOLOGICAL-STUDIES WITH THE SULFATE-REDUCING BACTERIUM DESULFOVIBRIO-DESULFURICANS - EVALUATION FOR USE IN A BIOFUEL CELL

The growth kinetics of the sulfate-reducing bacteria Desulfovibrio des ulfuricans Essex 6 was investigated under various conditions for poten tial use in a microbial fuel cell that recovers electrons generated fr om the reduction of sulfate to hydrogen sulfide. Hydrogen sulfide was Sound to inhibit growth and decrease both the growth yields and the su lfate-specific reduction rate. Hydrogen sulfide inhibition was direct, reversible, and not due to limitation by iron deficiency. A high init ial lactate concentration also retarded bacterial growth, reduced the specific sulfate reduction rates, and gave variable biomass growth yie lds. This effect resulted from a bottleneck in the lactate oxidation p athway which induced the production of the secondary product butanol. The use of pyruvate as a carbon source was more advantageous than lact ate in terms of growth rate and biomass growth yields, with only a sli ght decrease in the rate of specific sulfate reduction. For equal biom ass, a slightly higher current density was generated from lactate than pyruvate, but pyruvate required nearly 40% less sulfate.