Nitrogenase-Dependent Hydrogen Production by Cyanobacteria

Abstract

Cyanobacteria possess three different types of nitrogenases, two Mo- and one V-nitrogenases, all of which catalyse the reduction of the dinitrogen molecule to ammonia accompanied by the evolution of molecular hydrogen. V-nitrogenase is most effective in producing H-2 and is, therefore, suited for potential applications in solar energy conversion programs to generate molecular H-2 as a clean and renewable energy source. Intact cells of cyanobacteria often show rather little net H-2-production due to the concomitant H-2-consumption by uptake hydrogenase. The unicellular N-2-fixing Cyanothece is currently the focus of H-2-production research. Wild-type cyanobacteria are already capable of maximal H-2-production and any further enhancement of H-2-formation must be achieved by manipulating linear photosynthetic electron transport which is rate-limiting in light-and nitrogenase-dependent H-2-generation.