Efficient enzyme-catalyzed production of diosgenin: inspired by the biotransformation mechanisms of steroid saponins in Talaromyces stollii CLY-6

Abstract

Diosgenin is an important raw material of numerous synthetic steroidal drugs, such as sex hormones, contraceptives, and cortisone. Diosgenin production by enzymatic catalysis provides a solution for avoiding severe environmental issues caused by conventional acid hydrolysis. However, exploring high-efficiency enzymes and setting up catalytic processes still remain challenging. Herein, we identified a strain named Talaromyces stollii CLY-6, which showed efficient transformation of steroid saponins into diosgenin. Through genomic analysis and protein fingerprinting, two novel steroid saponin glycosidases (Rhase-TS: α-L-rhamnosidase; Gluase-TS: β-D-glucosidase) were discovered from Talaromyces stollii CLY-6. Enzyme over-expression and functional investigation suggested that Rhase-TS is capable of specifically hydrolyzing the terminal α-L-1,2-rhamnoside of steroid saponins, and Gluase-TS can release the residual glucose groups, thereby revealing a microbial transformation mechanism of steroid saponins and providing an enzymatic foundation for guiding diosgenin production. Notably, Rhase-TS exhibited excellent enzymatic properties with high thermostability (<70 °C), broad pH stability (pH 3.0 to 10.0), high rhamnose tolerance (K_i: 0.5 M), and high catalytic activity (136.34 U mg⁻¹). Inspired by the above studies, a whole-enzyme-catalyzed approach was explored and optimized to efficiently prepare diosgenin at the gram-level (up to 96.5% yield). Compared with conventional acid hydrolysis, this enzyme-based approach showed a significant advantage in reducing environmental pollution and increasing economic benefits, offering a promising alternative for green and eco-friendly diosgenin production.