稀有人参皂苷C-K转化菌株的筛选鉴定及其转化特性

Screening, Identification and Transformational Property of Minor Ginsenoside Compound K-Producing Fungus

以原人参二醇型皂苷混合物为底物对10种霉菌进行筛选,发现3.26号菌株能够将高含量的原人参二醇型皂苷Rb1、Rb2、Rc等转化为具有抗肿瘤活性的稀有人参皂苷Compound K(C-K)。经形态学和ITS序列分析鉴定,该菌株属于附球霉属(Epicoccum)真菌。从该菌株培养液中分离出人参皂苷水解酶粗酶E-I,确定其最适pH值和最适温度分别为pH 5.0和40℃。用EI分别转化人参皂苷Rb1和Rb2、Rc,发现它既能水解人参皂苷Rb1,也能水解Rb2和Rc,但是对Rb1的水解活性更强。上述结果说明:3.26号菌株产生的糖苷酶具有广泛的底物专一性,但是对葡萄糖苷键的专一性更高;该菌的生物转化途径为人参皂苷Rb1、Rb2、Rc→Rd→F2→C-K。

Ten fungi were screened with regard to their ability to convert major saponins Rbl, Rb2 and Rc to Compound K （C-K） which has notable anti-tumor activity. Among these,strain sp. 3.26 exhibited highest transfer ability. The strain sp. 3.26 was identified as Epicoccum sp. through ITS sequence analysis and morphology observation. A crude ginsenoside-hydrolyzing [3-glucosidase（E- I） was isolated from a culture filtrate of the strain sp. 3.26. The optimal pH and temperature of E-I were pH 5.0 and 40 ~C ,respectively. E-I not only hydrolyze ginsenoside Rbl but also hydrolyze Rb2 and Rc. However,E-I has higher activity to Rb〉 This result indicated that the glycosidases secreted by strain sp. 3.26 has wide substrate specificity,and was more specific to glucosidic linkage,and the biotransformation pathways by this strain was ：ginsenosides Rbl, Rb2, Rc→Rd→F2→C-K.