The biologically mediated water–gas shift reaction: structure, function and biosynthesis of monofunctional [NiFe]-carbon monoxide dehydrogenases

Among the possible renewable energies sources, biomass gasification has been considered one promising alternative to meet the daily growing energy demand. The outcome of this process is a synthetic gas (syngas) mainly composed of carbon monoxide and hydrogen. Syngas can be upgraded by a group of anaerobic micro-organisms, thanks to the biologically mediated water–gas shift (WGS) reaction. In this process, the conversion of CO and H2O into CO2 and H2 is catalyzed by two enzymes: carbon monoxide dehydrogenase (CODH) and hydrogenase. In order to efficiently use micro-organisms as a cost effective and environmentally friendly technology, it is fundamental to deeply understand how this process occurs. In this review paper, an overview on the possible biotechnological uses of the WGS reaction is presented, focusing mainly on the fundamental characterization of the CODH enzyme.