Influence of Energy and Electron Availability on In Vivo Methane and Hydrogen Production by a Variant Molybdenum Nitrogenase

A variant form of Mo nitrogenase catalyzes the conversion of CO2 and protons to the biofuels CH4 and H2 . A constant supply of electrons and ATP is needed to drive these reduction reactions. The bacteriumR. palustris generates ATP from light and has a versatile metabolism that makes it ideal for manipulating electron availability intracellularly. We therefore explored its potential as a biocatalyst for CH4 and H2 production. We found that intracellular ADP had a major effect on biofuel production, more pronounced than the effect caused by ATP. This is probably due to inhibition of nitrogenase activity by ADP. In general, the amount of CH4 produced by the variant nitrogenasein vivo was affected by electron availability much less than was the amount of H2 produced. This study shows the nature of constraints onin vivo biofuel production by variant Mo nitrogenase.