Engineered formate dehydrogenase from Chaetomium thermophilum, a promising enzymatic solution for biotechnical CO2 fixation

Objectives Formate dehydrogenases (FDHs) are NAD(P)H-dependent enzymes that catalyse the reversible oxidation of formate to CO2. The main goal was to use directed evolution to obtain variants of the FDH fromChaetomium thermophilum(CtFDH) with enhanced reduction activity in the conversion of CO(2)into formic acid. Results Four libraries were constructed targeting five residues in the active site. We identified two variants (G93H/I94Y and R259C) with enhanced reduction activity which were characterised in the presence of both aqueous CO(2(g))and HCO3-. The A1 variant (G93H/I94Y) showed a 5.4-fold increase in catalytic efficiency (k(cat)/K-M) compared to that of the wild-type for HCO(3)(-)reduction. The improved biocatalysts were also applied as a coupled cofactor recycling system in the enantioselective oxidation of 4-phenyl-2-propanol catalysed by the alcohol dehydrogenase fromStreptomyces coelicolorA3 (ScADH). Conversions in these reactions increased from 56 to 91% when the A1 variant was used instead of wild-typeCtFDH. Conclusions Two variants presenting up to five-fold increase in catalytic efficiency andk(cat)were obtained and characterised. They constitute a promising enzymatic alternative for CO(2)utilization and will serve as scaffolds to be further developed in order to meet industrial requirements.