The development of renewable fuels of the future is important for the replacement of
depleting oil and natural gas reserves. Hydrogen is one of the most promising clean fuels, since its
combustion yields only water. One of the visionary methods to obtain hydrogen at the expanse of solar
energy is the use of photosynthetic microorganisms. Hydrogen production in phototrophs is coupled to
the oxygenic and anoxygenic photosynthesis involving hydrogen-evolving enzymes, hydrogenases and
nitrogenases. At the present time the efficiency of hydrogen photoproduction is not sufficiently high.
Most hydrogen-evolving enzymes are inhibited by molecular oxygen, which creates a major barrier for
the sustained hydrogen photoproduction in oxygenic phototrophs, such as green algae and
cyanobacteria. However, several strategies have been applied to solve this problem, including spatial
and temporal separation of water splitting and hydrogen evolution, and regulation of water splitting
activity and respiration to maintain anoxic conditions. Anoxygenic photosynthesis can be used to drive
hydrogen photoproduction in integrated systems including fermentative anaerobic organisms. In this
review different mechanisms for hydrogen production in photosynthetic organisms and the latest
advances in this area are discussed.
Keywords: Hydrogen production, hydrogenases, nitrogenases, ferredoxin, photosystem I, photosystem II,
oxygen evolving complex, ATP, NADPH, Nostoc, Synechocystis, Gloeocapsa, Synechococcus, Spirulina
