Approaches to developing biological H2-photoproducing organisms and processes

Abstract

The development of efficient biological systems for the direct photoproduction of H2 gas from water faces several challenges, the more serious of which is the sensitivity of the H2-evolving enzymes (hydrogenases) to O2, an obligatory by-product of photosynthesis. This high sensitivity is common to both FeFe and NiFe hydrogenases, and is caused by O2 binding to their respective metallocatalytic sites. This overview describes approaches to (i) molecular engineering of algal FeFe-hydrogenase to prevent O2 access to its catalytic site; (ii) transform a cyanobacterium with an O2-tolerant bacterial NiFe hydrogenase or (c) partially inactivate algal O2-evolution activity to create physiologically anaerobiosis and induce hydrogenase expression.