Photobiocatalysis: the power of combining photocatalysis and enzymes.

Photobiocatalysts are constituted by a semiconductor with or without a light harvester that activates an enzyme. A logical source of inspiration for the development of photobiocatalysts has been natural photosynthetic centers. In photobiocatalysis, the coupling of the semiconductor and the enzyme frequently requires a natural cofactor and a relay transferring charge carriers from the semiconductor. The most widely studied photobiocatalysts so far make use of conduction band electrons of excited semiconductors to promote enzymatic reductions mediated by NAD(+) /NADH and an electron relay. The present review presents the state of the art in the field and has been organized based on the semiconductor and the reaction type including oxidations, hydrogen generation, and CO2 reduction. The possibility of direct enzyme activation by the semiconductor and the influence of the nature of mediator are also discussed as well as the use of mimics of the enzyme active center in combination with the semiconductor. The final section summarizes the state of the art of photobiocatalysis and comments on our view on future developments of the field.