Elevated conversion of CO2 to versatile formate by a newly discovered formate dehydrogenase from Rhodobacter aestuarii

•RaFDH is newly discovered through genome-mining and phylogenetic analysis.•The recombinant RaFDH was characterized as a CO2 reductase under aerobic condition.•In particular, RaFDH-driven CO2 reduction far surpassed formate oxidation. Due to climate change, recent research interests have increased towards CO2 utilization as a strategy to mitigate the atmospheric CO2 level. Herein, we aimed to explore formate dehydrogenases (FDHs) from chemoautotroph to discover an efficient and O2-tolerant biocatalyst for catalyzing the CO2 reduction to a versatile formate. Through genome-mining and phylogenetic analysis, the FDH from Rhodobacter aestuarii (RaFDH) was newly discovered as a promising O2-tolernat CO2 reductase and was successfully expressed in Escherichia coli. In this study, the optimum conditions and turnover rates of RaFDH were examined for CO2 reduction and formate oxidation. In particular, the RaFDH-driven CO2 reduction far surpassed the formate oxidation with a turnover rate of 48.3 and 15.6 min−1, respectively. The outstanding superiority of RaFDH towards CO2 reduction can be applicable for constructing a feasible electroenzymatic system that produce a versatile formate from CO2 as a cheap, abundant, and renewable resource.