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

• Published in: Applied and Environmental Microbiology 2010-12, Vol.76 (23), p.7717-7722
• Main Authors: Huang, Jean J, Heiniger, Erin K, McKinlay, James B, Harwood, Caroline S
• Format: Article
• Language: English
• Subjects: Acetates - metabolism; Acetic acid; Bicarbonates - metabolism; Biodiesel fuels; Biological and medical sciences; Biomass; Cell culture; Cells; Electrons; Fundamental and applied biological sciences. Psychology; Gases - metabolism; Gram-negative bacteria; Hydrogen - metabolism; Light; Microbiology; Nitrogen - metabolism; Nitrogenase - metabolism; Oxidation-Reduction; Physiology; Rhodopseudomonas - metabolism; Rhodopseudomonas palustris; Succinic Acid - metabolism; Thiosulfates - metabolism
• ISSN: 0099-2240; 1098-5336; 1098-6596
• DOI: 10.1128/AEM.01143-10

A challenge for photobiological production of hydrogen gas (H₂) 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 H₂ 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 H₂ 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 H₂. H₂ production with acetate and succinate as electron donors was less efficient (40 to 60%), partly because nongrowing cells excreted the intermediary metabolite α-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 H₂ production. The possibility to use thiosulfate expands the range of electron-donating compounds for H₂ production by PNSBs beyond biomass-based electron donors.