Photobiological hydrogen-producing systems

Hydrogen photoproduction by micro-organisms combines the photosynthetic properties of oxygenic and non-oxygenic microbes with the activity of H-2-producing enzymes in nature: hydrogenases and nitrogenases. The overall efficiency of the process depends on the separate efficiencies of photosynthesis and enzymatic catalysis. This tutorial review discusses the biochemical pathways for H-2 production in different organisms, barriers to be overcome, and possible suggestions for integrating photobiological H-2 production with fermentative, anaerobic systems for a potentially more efficient process.