Novel FeruloylEsterase from <i>Rehmannia glutinosa</i> Endophyte <i>Alternaria botrytis</i> RYF1 and Its Applicationin the Production of Verbasoside and Hydroxysalidroside

Verbasoside and hydroxysalidroside are derivatives of phenylethanol glycosides (PhGs) that exhibit a range of pharmacological activities and also serve as valuable precursors for synthesizing other more complex PhGs. However, chemical synthesis and plant extraction for large-scale production are impractical to date. Here, 79 fungi from four types of PhG-containing plants and their rhizospheric soils were screened out, and endophyte Alternaria botrytis RYF1 from Rehmannia glutinosa was identified with the ability to generate verbasoside from decaffeoyl acteoside. To mine the key enzymes concerning the biotransformation, RNA-seq was carried out on RYF1 and RSF6, from which novel feruloyl esterase DN417 was captured. DN417 possesses hydrolyzing capabilities toward several PhGs. DN417’s ability to produce verbasoside was tested in a 5 L fermenter, yielding 50.37 g/L of verbasoside with a conversion rate of 94.51% from crude acteoside. Finally, a dual-enzyme synergy involving feruloyl esterase and rhamnosidase was designed to produce hydroxysalidroside. After optimization of the enzyme ratios and pH, the approach successfully yielded hydroxysalidroside at a concentration of 13.60 g/L with a conversion rate of 81.30%. The study is the first report on the feruloyl esterase for the PhGs and also laid a solid foundation for the production of value-added compounds of PhGs.