Characterization of a novel D-sorbitol dehydrogenase from Faunimonas pinastri A52C2

The enzyme D-sorbitol dehydrogenase (SLDH) facilitates the conversion of D-sorbitol to L-sorbose. While current knowledge of this enzyme class predominantly centers on Gluconobacter oxydans, the catalytic properties of enzymes from alternative sources, particularly their substrate specificity and coenzyme dependency, remain ambiguous. In this investigation, we conducted BLASTp analysis and screened out a novel SLDH (Fpsldh) from Faunimonas pinastri A52C2. The SLDH was then identified and characterized. Analysis of the purified enzyme revealed its dependence on NAD⁺/NADP⁺ and its specificity for L-sorbose production. Fpsldh demonstrated sustained catalytic activity over temperatures ranging from 27 to 37 ℃, with optimal performance observed at pH 8.0-10.0, and it exhibited no requirement for metal ions for activation. The K_m of Fpsldh is 7.51 mM. Furthermore, a Bacillus licheniformis host expressing Fpsldh was engineered. The resultant whole-cell catalyst yielded 13.19 g/L of L-sorbose after 33.6 h of transformation, obviating the need for exogenous cofactors. This study enhances our understanding of the catalytic properties of the SLDH family and introduces a novel method for L-sorbose production, a compound of considerable commercial value. KEY POINTS: •New D-sorbitol dehydrogenase from Faunimonas pinastri A52C2 is characterized. •Fpsldh is not PQQ but NAD⁺/NADP⁺-dependent. •Bacillus licheniformis expressing Fpsldh can produce 13.19 g/L L-sorbose within 33.6 h.