Insights into Enzyme Reactions with Redox Cofactors in Biological Conversion of CO.

Carbon dioxide (CO) is the most abundant component of greenhouse gases (GHGs) and directly creates environmental issues such as global warming and climate change. Carbon capture and storage have been proposed mainly to solve the problem of increasing CO concentration in the atmosphere; however, more emphasis has recently been placed on its use. Among the many methods of using CO, one of the key environmentally friendly technologies involves biologically converting CO into other organic substances such as biofuels, chemicals, and biomass via various metabolic pathways. Although an efficient biocatalyst for industrial applications has not yet been developed, biological CO conversion is the needed direction. To this end, this review briefly summarizes seven known natural CO fixation pathways according to carbon number and describes recent studies in which natural CO assimilation systems have been applied to heterogeneous in vivo and in vitro systems. In addition, studies on the production of methanol through the reduction of CO are introduced. The importance of redox cofactors, which are often overlooked in the CO assimilation reaction by enzymes, is presented; methods for their recycling are proposed. Although more research is needed, biological CO conversion will play an important role in reducing GHG emissions and producing useful substances in terms of resource cycling.