Desulfovibrio vulgaris Growth Coupled to Formate-Driven H₂ Production

Formate is recognized as a superior substrate for biological H₂ production by several bacteria. However, the growth of a single organism coupled to this energetic pathway has not been shown in mesophilic conditions. In the present study, a bioreactor with gas sparging was used, where we observed for the first time that H₂ production from formate can be coupled with growth of the model sulfate-reducing bacterium Desulfovibrio vulgaris in the absence of sulfate or a syntrophic partner. In these conditions, D. vulgaris had a maximum growth rate of 0.078 h^-1 and a doubling time of 9 h, and the δG of the reaction ranged between -21 and -18 kJ mol^-1. This is the first report of a single mesophilic organism that can grow while catalyzing the oxidation of formate to H₂ and bicarbonate. Furthermore, high volumetric and specific H₂ production rates (125 mL L^-1 h^-1 and 2500 mL g_dcw^-1 h^-1) were achieved in a new bioreactor designed and optimized for H₂ production. This high H₂ production demonstrates that the nonconventional H₂-producing organism D. vulgaris is a good biocatalyst for converting formate to H₂.