Enzymatic transformation of ginsenoside Rg3 to Rh2 using newly isolated Fusarium proliferatum ECU2042

A new soil isolate, Fusarium proliferatum ECU2042, was found capable of producing a ginsenoside Rg3 hydrolase (a special β-glucosidase) which is useful for production of a very potent antitumor agent Rh2. By investigating its fermentation progress, the optimal time for β-glucosidase biosynthesis was determined as 72 h. The crude β-glucosidase was partially purified by 49.4-fold from the cell-free extract with an activity yield of 13%. The catalytic performance of the partially purified β-glucosidase was examined, giving optima of pH and temperature at pH 5.0–6.0 and 50 °C. It was found that the F. proliferatum β-glucosidase can also hydrolyze cellobiose, but not active towards a frequently used artificial substrate p-nitrophenyl β-d-glucopyranoside (pNPG). In a lab-scale preparation, the bio-hydrolytic reaction was carried out at 50 °C for 24 h in 50 ml NaAc/HAc buffer (100 mM, pH 5.0) containing 50 mg Rg3 and 12 mg lyophilized crude enzyme extract, giving the ginsenoside Rh2 in 60.3% conversion.