Microbial conversion of ruscogenin by Gliocladium deliquescens NRRL1086: glycosylation at C-1

Abstract

The glycosylation of ruscogenin (1) by Gliocladium deliquescens NRRL 1086 was observed and gave a regioselectively glycosylated product identified as ruscogenin 1-O-beta-D-glucopyranoside (2) by infrared, mass spectrometry, and nuclear magnetic resonance spectra. Time-course studies indicated that it appeared to be favorable to accumulate 2 when ruscogenin was added to the 24-h-old stage II culture, and the yield of 2 was about 20.1% during 120 approximately 168 h. It was noted that additional carbohydrates could significantly increase glycoside formation and the yield of 2 even reached as high as 68% compared with the control 20.1%. The primary investigation about the characteristics of the enzyme resulted that the reaction was blocked by beta-glycosidase inhibitor imidazole, however, was enhanced remarkably by glycosyltransferase inhibitor sodium dodecyl sulfate. To our knowledge, this is the first reported case of producing steroidal saponin by microbial transformation, and G. deliquescens NRRL1086 would be a practical and highly efficient tool in producing natural ruscogenin monoside.