Photobiological hydrogen production and nitrogenase activity in some heterocystous cyanobacteria

Publisher Summary This chapter discusses the activities of nitrogenase and H 2 evolution in three cyanobacterial strains and some factors that affected these activities. Nitrogen-fixing heterocystous cyanobacteria are potential candidates for the development of photobiological hydrogen production systems. They produce H 2 under aerobic conditions using water as an electron donor. For example A. variabilis IAM M-58 was most active in H 2 production, and the amount of H 2 produced was markedly higher than that of the other species. Hydrogen metabolism in these cyanobacteria involves at least three enzymes: nitrogenase, uptake hydrogenase, and bidirectional hydrogenase. Some researchers favor hydrogenase over nitrogenase as the hydrogen evolving system because of its high energy efficiency, but it was reported that continued production of H 2 in air was mediated by nitrogenase in the heterocysts. To develop the hydrogen producing systems by cyanobacteria based on nitrogenase activity, it is important to find cyanobacterial strains which have a high activity of H 2 production.