Feilong Li / VTT Technical Research Centre of Finland, Espoo, Finland, Department of Bioproducts and Biosystems, Aalto University, 02150 Espoo, Finland
Michael Lienemann / VTT Technical Research Centre of Finland, Espoo, Finland
Topic: Enzyme Engineering
Metal-dependent formate dehydrogenases are potent biocatalysts for the reversible interconversion of CO2 and formate but their efficient engineering is precluded by their oxygen sensitivity. The E. coli formate hydrogenlyase (FHL) complex promotes cell growth by deacidifying the cytosol under anaerobic conditions with an oxygen-sensitive formate dehydrogenase (FDH) as an electron-input model. By using an FDH-deficient strain, we demonstrate that the growth inhibition by acidic glucose fermentation products can be alleviated by FHL complementation. Based on this principle, we present an effective and simple growth-based screening strategy to identify active FDH variants. Our screening concept was combined with a colorimetric assay and tested by screening of an FDH variant library comprised of 1032 FDH variants. This single-round screening identified variant A12G as an improved FDH version with a 90% increased formate oxidation rate when compared to the wildtype enzyme.
