Simultaneous transformation of ginsenoside Rb1 into rare ginsenoside F2 and Compound K by the extracellular enzyme from Aspergillus Niger Wu-16

Abstract Ginsenoside Compound K (CK) has high pharmacological activity for being widely used in the treatment and prevention of diseases. However, the content of CK in ginseng is very low or almost non-existent. In the present study, ginsenoside Rb1 was converted into ginsenoside F2 and CK by using the extracellular protein isolated from Aspergillus niger Wu-16. The results show that the crude enzymes produced by Wu-16 can catalyze the conversion of the substrate Rb1 to ginsenoside F2 and CK. The reaction time, pH, temperature, and ratio of enzyme to substrate for preparing ginsenoside F2 and CK were used as optimization factors. A reaction time of 48 h, pH=3, temperature of 55°C, and enzyme-to-substrate ratio of 0.8 were obtained. Furthermore, response surface optimization experiment was carried out to further obtain the maximum conversion rates of ginsenoside F2 and CK with 50.11% and 33.50% for 48 h, respectively. On this basis, the effect of metal ions on the enzymatic reaction showed that the conversion rate of ginsenoside Rb1 was increased remarkably by Co2+ with concentrations of 0.5 mM, and the highest conversion rate into rare ginsenoside CK reached 56.10%. Therefore, the advantage of enzymes catalysis from A. Niger Wu-16 could be a simple, convenient, and rapid method to produce rare saponin F2 and CK, this method provides a certain reference value for the production of rare ginsenosides.