Biotransformation of mogrosides from Siraitia grosvenorii by Ganoderma lucidum mycelium and the purification of mogroside III E by macroporous resins

Abstract Mogrosides are the major triterpenoidal saponins found in swingle, the fruit of Siraitia grosvenorii , which have recently been widely used throughout the world as natural food sweeteners. Among this class of compounds, mogroside III E (MG III E) exhibits the most intense sweetness, and it was also found to effectively regulate blood glucose levels. However, the relative abundance of naturally occurring MG III E is low compared to other mogrosides. Therefore, the purpose of this study was to enrich MG III E through biotransformation of fruit extracts and to develop a reliable method for its purification. We used HPLC coupled with mass spectrometry and nuclear magnetic resonance spectroscopy for metabolite analysis and identified MG III E as a major metabolite of Ganoderma lucidum mycelium. This organism converts the most abundant mogroside, mogroside V, to MG III E via a deglycosylation reaction; high levels of β -glucosidase activities were also detected. In addition, we established an efficient purification method for MG III E using HP-20 macroporous resin. Optimization of the method was accomplished by kinetic model fitting, dynamic adsorption studies, and desorption experiments. The purity of MG III E was increased from 11.71% to 54.19%, with a 70%–76% recovery rate, and the scaled-up purification process allowed us to harvest 17.38 g of MG III E with 55.14% purity and a 74.71% of recovery rate. Therefore, our low cost, time-saving, easy to scale-up procedure for isolating MG III E could be applicable in industrial processes.