Electron transfer pathways of formate-driven H2 production in Desulfovibrio

Abstract

The potential of sulfate-reducing bacteria (SRB) as biocatalysts for H2 production from formate was recently demonstrated, but the electron transfer pathways involved were not described. In the present work, we analyzed the H2 production capacity of five Desulfovibrio strains: Desulfovibrio vulgaris, Desulfovibrio desulfuricans, Desulfovibrio alaskensis, Desulfovibrio fructosivorans, and Desulfovibrio gigas. D. vulgaris showed the highest H2 productivity (865 mL Lmedium (-1)), and D. gigas the lowest one (374 mL Lmedium (-1) of H2). The electron transfer pathways involved in formate-driven H2 production by these two organisms were further investigated through the study of deletion mutants of hydrogenases (Hases) and formate dehydrogenases (Fdhs). In D. vulgaris, the periplasmic FdhAB is the key enzyme for formate oxidation and two pathways are apparently involved in the production of H2 from formate: a direct one only involving periplasmic enzymes and a second one that involves transmembrane electron transfer and may allow energy conservation. In the presence of selenium, the Hys [NiFeSe] Hase is the main periplasmic enzyme responsible for H2 production, and the cytoplasmic Coo Hase is apparently involved in the ability of D. vulgaris to grow by converting formate to H2, in sparging conditions. Contrary to D. vulgaris, H2 production in D. gigas occurs exclusively by the direct periplasmic route and does not involve the single cytoplasmic Hase, Ech. This is the first report of the metabolic pathways involved in formate metabolism in the absence of sulfate in SRB, revealing that the electron transfer pathways are species-specific.

Reversible and Selective Interconversion of Hydrogen and Carbon Dioxide into Formate by a Semiartificial Formate Hydrogenlyase Mimic

“…21,22 Desulfovibrio vulgaris Hildenborough can grow by converting formate to H 2 , 23 with formate oxidation catalyzed by a periplasmic FDH, and H 2 produced either via direct (periplasmic H 2 ase) or transmembrane electron transfer (cytoplasmic H 2 ase). 24…”

“…In D. vulgaris cells, the two periplasmic enzymes exchange electrons through the type-I cytochrome c 3 (TpI c 3 ) electron acceptor. 24 We therefore studied the activity of these enzymes in solution with TpI c 3 . A high concentration of the cytochrome (1.9 μM, 100-fold excess vs FDH) was required to achieve comparable kinetics of H 2 and formate production (Figure S11a,b), revealing the superiority of coimmobilizing the two enzymes on synthetic ITO NPs to achieve efficient electron transfer.…”

Potential of Autochthonous Sulfate-Reducing Microbial Communities for Treating Acid Mine Drainage in a Bench-Scale Sulfidogenic Reactor

“…The small cultivation period of the FOR 7 reactor is due to the oxidation of the enrichment medium after the 10-day experimental period. This can probably be explained by H 2 production after the initial sulfate consumption, as observed by Martins et al (2016). It is important to emphasize that, despite this inferior enrichment period, sulfate removal in the FOR 7 reactor (~18 mM) was close to that of the LAC 7 and ETA 7 reactors (20 mM and 24 mM, respectively).…”

Effects of set cathode potentials on microbial electrosynthesis system performance and biocathode methanogen function at a metatranscriptional level

“…Desulfovibrio sp., which were present in low relative abundance on the biocathodes (Fig. 1), have also been shown to be capable of using formate to produce H 2 in the absence of sulfate 75,76 . Unfortunately, these species could not be resolved into bins by the metagenomic analysis for further investigation.…”