Rational Design of Formate Dehydrogenase for Enhanced Thermal Stability and Catalytic Activity in Bioelectrocatalysis

Formate dehydrogenase can be utilized as a biocatalyst in the bioelectrocatalysis of converting CO₂ into formic acid. However, its industrial application has been hindered by limited thermal stability. This study successfully obtained a mutant (D533S/E684I) with enhanced thermal stability and catalytic activity through the rational design of flexible regions. The mutant exhibited a half-life (t_1/2) 1.5 times longer than the wild type (WT) at 35 °C, along with a specific enzyme activity 7.46 times higher than that of the WT. Additionally, the catalytic efficiency (k_cat/K_m value) of the mutant toward the substrate was 2.72 s^-1·mM^-1, representing a 19.4-fold increase compared to the WT (0.14 s^-1·mM^-1). Formic acid production reached 53.4 mM through bioelectrocatalysis after 10 h, utilizing the mutant as the biocatalyst. Molecular dynamics simulations and structural analysis were employed to investigate the molecular mechanisms behind the enhanced thermal stability and activity. The displacement of a highly flexible region in the mutant may counteract the stability-activity trade-off. This study proposed a method for improving both thermal stability and activity in enzyme evolution.