Cyanobacteria and Photosynthetic Bacteria: Metabolic Engineering of Hydrogen Production

Photobiological hydrogen production are light driven processes that either use water as a source of electrons cyanobacteria, or organic acids, during photo fermentative hydrogen production by purple no sulfur photosynthetic bacteria. Hydrogen evolution in these organisms is largely catalyzed by nitrogenase, with ATP being required. Although hydrogen is also produced by dark fermentation, photobiological hydrogen production has the advantage that it is driven by solar energy conversion. On the other hand, photobiological hydrogen production also suffers from practical limitations: sensitivity of hydrogenase to oxygen, hydrogen consumption driven by respiration, competition for electrons with carbon dioxide fixation, saturation of hydrogen production at low light intensities, as well as an incomplete understanding of the metabolic networks involved in hydrogen metabolism and the unavailability of genetic and molecular tools for improvement in many species. Here we summarize the use of metabolic engineering to increase photobiological hydrogen production.