Biohydrogen production by a novel strain Petroclostridium sp. X23 isolated from the production water of oil reservoirs

Biohydrogen production from H2-producing has been considered a promising alternative for the replacement of fossil fuels. However, the mechanisms that affect the H2-producing capacities of wild-type strains remain largely elusive. To explore the capabilities of biohydrogen production from microorganisms in the deep subsurface oil-reservoir environment, we isolated an H2-producing bacteria identified as the genus Petroclostridium from a long-term methanogenic crude oil-degrading enrichment culture of the production water from oil reservoir. The impact of various temperature, pH, and glucose concentrations on hydrogen production by Petroclostridium sp. X23 was investigated. Under the conditions of 37 °C, initial pH 8.0, and glucose concentration of 4 g/L, the strain X23 achieved its maximum hydrogen yield at 1.82 ± 0.12 mol H2/mol glucose. When compared to the previously reported strain SK-Y3, X23 exhibited enhanced H2-producing ability, with lesser energy biomass production. Comparative genomic analysis revealed that the genome of X23 contains more genes associated with hydrogen generation than SK-Y3. These findings proposed Petroclostridium sp. X23 is a potential candidate for dark fermentative hydrogen production under alkaline and mesophilic conditions. It also increased our knowledge of genotypes related to high H2-producing capability, which may provide instructions for future selection of high-yielding strains and reasonable metabolic engineering of wild-type H2-producing strains.