Hydrogen Gas Production By a Species of Ectothiorhodospira

A hydrogen gas (H₂) producing species of Ectothiorhodospira isolated from Soap Lake, Washington, possessed the nitrogenase enzyme complex. Increasing evolution of H₂ with decreasing ammonium chloride (NH₄C1) concentrations provided evidence that nitrogenase was the catalyst in gas production. Cells were grown in a mineral medium plus 0.2% acetate with sodium sulfide (Na₂S*9H₂0) as electron donor. Syringes inserted into 27 ml stoppered tubes were used to collect the gas. Factors increasing H₂ production included addition of poor nitrogen sources such as glutamic acid, alanine, and serine; addition of reduced carbon compounds such as propionate and succinate; increasing reducing power by increasing sodium sulfide concentration; and increasing the energy charge (ATP) by increasing light intensity. The use of phototrophs in waste treatment with the production of useful by-products such as H₂ is of interest in industrial research