Biotransformation of notoginsenoside Fe into compound K by β-glucanase: Mechanistic insights

Rare ginsenoside compound K (CK) exhibits diverse biological activities, but its low natural abundance limits its broader utilization. In this study, notoginsenoside Fe was used as the substrate for β-glucanase-mediated enzymatic production of CK, and the associated enzyme-substrate interactions were investigated. HPLC monitoring showed a sequential biotransformation pattern of Fe→Mc→CK. Single-factor experiments identified suitable reaction conditions of 55 °C, 72 h, a substrate-to-enzyme mass ratio of 3:1, and pH 3.2. Subsequent optimization using a Box-Behnken response surface design predicted optimal conditions of pH 3.27, a substrate-to-enzyme ratio of 2.98:1, and 55.62 °C. Verification experiments under these conditions yielded a CK molar yield of 83.89 ± 1.37%. Spectroscopic analyses provided evidence of interactions between notoginsenoside Fe and β-glucanase. Molecular docking and molecular dynamics simulations further suggested plausible binding modes in which the glycosyl moieties of the ligands interact with residues in the predicted binding pocket through hydrogen-bonding and hydrophobic contacts. These findings provide experimental data for β-glucanase-mediated CK production and molecular-level insights into β-glucanase-ginsenoside interactions.