关键词: 蛹虫草；β-葡萄糖苷酶；α-L-阿拉伯呋喃糖苷酶；人参皂苷

Abstract: In this study, a strain of Cordyceps militaris with high productivity of β-glucosidase was identified and selected. The effects of carbon source, nitrogen source and pH value on the production of β-glucosidase, α-L-arabinofuranosidase, cordyceps acid and biomass by the strain were studied to determine the optimal culture conditions for the production of bioactive substances with high productivity. The transformation pathways and efficiency of ginsenosides Rg1 and Rc by C. militaris were evaluated. The activities of β-glucosidase and α-L-arabinofuranidase were determined by ultraviolet (UV) spectrophotometry. The ginsenoside composition of the transformed products was identified by ultra-high performance liquid chromatography-quadrupole time-of-flight mass spectrometry (UPLC-Q-TOF-MS), and the content of cordycepin and the transformation efficiency of ginsenoside were determined by high performance liquid chromatography (HPLC). The results showed that the highest β-glucosidase activity of ((74.70 ± 0.09) U/mL) was obtained after 120 h culture using cellulose disaccharide as the carbon source and beef extract as the nitrogen source at pH 8, while the highest α-L-arabinofuranosidase activity of ((11.55 ± 0.01) U/mL) was obtained after 72 h culture using lactose as the carbon source and peptone as the nitrogen source at pH 4. The transformation pathways of ginsenoside Rg1 by C. militaris were Rg1→Rh1 and Rg1→F1, and the transformation pathways of Rc were Rc→Rd→Rg3→CK and Rc→CMc. The conversion efficiency of ginsenoside Rg1 and Rc was 54.9% and 83.44% after 168 h, respectively. This study provides a theoretical basis to improve the efficiency of biotransformation of ginsenoside by the medicinal and edible fungus C. militaris, and lays theoretical support for developing food and medicinal products from C. militaris and ginseng.

Key words: Cordyceps militaris; β-glucosidase; α-L-arabinofuranosidase; ginsenoside