Production of Hydrogen Gas from Light and the Inorganic Electron Donor Thiosulfate by Rhodopseudomonas palustris

Abstract

A challenge for photobiological production of hydrogen gas (H 2 ) as a potential biofuel is to find suitable electron-donating feedstocks. Here, we examined the inorganic compound thiosulfate as a possible electron donor for nitrogenase-catalyzed H 2 production by the purple nonsulfur phototrophic bacterium (PNSB) Rhodopseudomonas palustris. Thiosulfate is an intermediate of microbial sulfur metabolism in nature and is also generated in industrial processes. We found that R. palustris grew photoautotrophically with thiosulfate and bicarbonate and produced H 2 when nitrogen gas was the sole nitrogen source (nitrogen-fixing conditions). In addition, illuminated nongrowing R. palustris cells converted about 80% of available electrons from thiosulfate to H 2 . H 2 production with acetate and succinate as electron donors was less efficient (40 to 60%), partly because nongrowing cells excreted the intermediary metabolite ␣-ketoglutarate into the culture medium. The fixABCX operon (RPA4602 to RPA4605) encoding a predicted electron-transfer complex is necessary for growth using thiosulfate under nitrogen-fixing conditions and may serve as a point of engineering to control rates of H 2 production. The possibility to use thiosulfate expands the range of electron-donating compounds for H 2 production by PNSBs beyond biomass-based electron donors.

Microbial mutualism dynamics governed by dose-dependent toxicity of cross-fed nutrients

“…Final cell densities and all serum vial readings were taken in cuvettes and samples were diluted as necessary to achieve values below 1 OD 660 . H 2 was quantified using a Shimadzu (Kyoto, Japan) gas chromatograph as described (Huang et al, 2010). Glucose, organic acids, and ethanol were quantified using a Shimadzu high-performance liquid chromatograph (HPLC) as described (McKinlay et al, 2005).…”

A Rhodopseudomonas palustris nifA* mutant produces H2 from -containing vegetable wastes

“…The amount of H 2 produced by the wild type in this condition was noticeably higher than the amount produced by the mutant; this can be attributed to the fact that NH þ 4 had been consumed at the moment H 2 production started, so the electrons deriving from acetate were all diverted to H 2 rather than biosynthesis, as previously described [18].…”

“…Analytical methods H 2 was quantified by gas chromatography as indicated in [18]. Organic acids and culture supernatants were analyzed by HPLC as in [18].…”

“…Organic acids and culture supernatants were analyzed by HPLC as in [18]. The NH þ 4 content of VWD medium was determined with Nessler method [19].…”

Breakdown of food waste by anaerobic fermentation and non-oxygen producing photosynthesis using a photosynthetic bacterium

“…Hydrogen gas can also be produced photosynthetically. Non-sulphur purple bacterial such Rhodopseudomonas palustris can use light and both organic carbon compounds and the inorganic electron donor thiosulfate as suitable electron-donating feedstocks and have been intensively studied for photobiological production of hydrogen gas as a potential biofuel (Larimer et al, 2004;Huang et al, 2010). H 2 is a potential alternative to gasoline for use as a transportation fuel in conjunction with hydrogen fuel cells because it has a high energy content.…”