Microbial transformation of saponins in Dioscorea zingiberensis for diosgenin production with Trichoderma reesei

Microbial transformation of plant tubers for diosgenin production is an attractive clean method in industry. The purpose of this study was to evaluate the quality of the product obtained this way. Changes of saponins during the hydrolysis of Dioscorea zingiberensis tubers by Trichoderma reesei were investigated. Four main saponins were isolated from the plant herbs. Sugar chains, which connected to the C-3 hydroxyl group in saponins, were cleaved stepwisely by Trichoderma reesei from the terminal sugar until the aglycone was released. Diosgenin-3-O-beta-D-glucose was a byproduct in this process. While, in the petrol extract of the microbial hydrolyzate, only diosgenin was detected. Melting point, IR. spectra and C-13 NMR. spectroscopy were used to estimate the quality of the product. Diosgenin obtained from bioconversion showed similar characteristic to that from acid hydrolyzation, confirming microbial transformation was an effective method for diosgenin production.