Hydrogenases for biological hydrogen production

Biological H-2 production offers distinctive advantages for environmental protection over existing physico-chemical methods. This study focuses specifically on hydrogenases, a class of enzymes that serves to effectively catalyze H-2 formation from protons or oxidation to protons. It reviews the classification kschemes (i.e. [NiFe]-, [FeFe]-, and [Fe]-hydrogenases) and properties of these enzymes, which are essential to understand the mechanisms for H-2 production, the control of cell metabolism, and subsequent increases in H-2 production. There are five kinds of biological hydrogen production methods, categorized based upon the light energy requirement, and feedstock sources. The genetic engineering work on hydrogenase to enhance H-2 production is reviewed here. Further discussions in this study include nitrogenase, an enzyme that normally catalyzes the reduction of N-2 to ammonia but is also able to produce H-2 under photo-heterotrophic conditions, as well as other applicable fields of hydrogenase other than H-2 production. (C) 2011 Elsevier Ltd. All rights reserved.