Photobiological production of hydrogen gas as a biofuel

Solar energy can be converted into chemical energy in the form of hydrogen gas using oxygenic and anoxygenic photosynthetic microbes. Laboratory-scale measurements suggest that photobiological hydrogen production rates could yield more energy than current crop-based biofuel productivities. Major challenges, such as inhibitory amounts of oxygen produced during oxygenic photosynthesis and inhibition of H2-producing nitrogenase by ammonia, are being overcome through genetic engineering. Further advances are expected as the metabolic and regulatory aspects behind photobiological hydrogen production are revealed. Genetic engineering, coculturing, and bioreactor designs making use of immobilized cells have the potential to increase conversion efficiencies of light energy to H2 and to decrease the land area needed for photobiological H2 production.