Biocatalytic methane oxidation

Abstract

The direct oxidation of methane to methanol using biocatalysts represents a groundbreaking advancement in effective natural gas utilization and methane valorization. The biological conversion of methane gas to methanol, which can serve as carbon feedstock, presents a significant economic opportunity. In nature, methane monooxygenases (MMOs), in both soluble and particulate forms, selectively oxidize methane to methanol. MMOs exhibit low activity, complexity, and are not readily tractable for recombinant expression in industrial microbial hosts. Achieving high volumetric productivities of methanol from methane requires functionally faster methane-converting enzymes, which has remained a major challenge in the field of methane oxidation. In this study, we report the discovery of the first cytochrome P450 from Caldimonas thermodepolymerans (CtCYP116B, i.e., CYP116B144), which is heterologously and highly expressed in Escherichia coli, and demonstrates the ability to directly convert methane to methanol. CtCYP116B exhibited the highest methane oxidizing activity (total turnover number of 606), surpassing other methane-converting enzymes. Furthermore, multi-enzyme cascade reactions using CtCYP116B, methanol dehydrogenase, and carboligases successfully produced C3−C4 chemicals from methane gas in vitro. The utilization of these functionally heterologously expressed CtCYP116B enzymes provide a powerful approach, serving as a key step in the construction of synthetic methanotrophs with significant biotechnological potential.