Photobiological hydrogen-producing systems.

Hydrogen photoproduction by micro-organisms combines the photosynthetic properties of oxygenic and non-oxygenic microbes with the activity of H2-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 H2 production in different organisms, barriers to be overcome, and possible suggestions for integrating photobiological H2 production with fermentative, anaerobic systems for a potentially more efficient process.