Sulfide product inhibition of Desulfovibrio desulfuricans in batch and continuous cultures

Abstract

Sulfide product inhibition kinetics for growth and activity of Desulfovibrio desulfuricans was investigated in batch and continuous cultures at pH = 7.0. A non-competitive inhibition model adequately described sulfide product inhibition kinetics. Inhibition coefficient ( K i) for maximum specific growth rate ( μ inh max) was 251 mg l −1 S in a batch experiment. Cell yield determined in a chemostat was reduced in half by a sulfide concentration of about 250 mg l −1 S, which was very close to the K i value for the batch growth. Maximum specific growth rate ( μ inh max) and cell yield ( Y c Lac ) were strongly inhibited by high levels of sulfide concentrations, whereas specific lactate utilization rate increased with increasing sulfide concentrations. The results indicated an increase in the relative energy needed for maintenance to overcome sulfide inhibition and uncoupling growth from energy production. However, D. desulfuricans to some extent could recover from the shock of high sulfide concentrations. Stoichiometry for catabolic reactions (energy producing) did not change at high sulfide concentrations, while anabolic reactions (cellular synthesis) were strongly inhibited by high sulfide concentrations. These results suggested that separation of sulfide product inhibition into growth (cell yield) and activity (substrate utilization rate) was important to incorporate the sulfide product inhibition kinetics in a variety of applications.