一株桑树内生真菌的分离及胞外多糖活性测定

Isolation of an Endophytic Fungus from Mulberry and Determination of Its Exopolysaccharide Activity

采用组织分离法从桑树枝条中分离获得一株内生真菌HZ-MB13,其代谢产物具有α-葡萄糖苷酶抑制活性和抗氧化活性。根据形态学特征和ITS序列分析,将HZ-MB13菌株鉴定为毛栓菌Trametes hirsuta。研究发现,HZ-MB13菌株产生的具有α-葡萄糖苷酶抑制活性和抗氧化活性的产物是胞外多糖。采用单因素法优化HZ-MB13菌株产胞外多糖的碳氮源和部分发酵条件:以40 g/L果糖为碳源,以20 g/L玉米浆为氮源,摇瓶装液量125 mL,初始pH 5.5,摇床转速150 r/min。在此条件下,HZ-MB13菌株的胞外多糖产量为(7.30±0.25)g/L。采用醇沉法分离HZ-MB13菌株发酵液中的胞外多糖,测定其α-葡萄糖苷酶抑制活性和抗氧化活性,结果显示HZ-MB13菌株的胞外多糖具有较明显的α-葡萄糖苷酶抑制活性,IC50值为7.53mg/mL;而且具有较好的抗氧化活性,对DPPH和ABTS自由基的清除活性高。研究结果为利用桑树内生真菌发酵生产糖尿病防治药物提供了理论依据。

An endophytic fungus strain HZ-MB13 withα-glucosidase inhibitory activity and antioxidant activity was isolated from mulberry branches by tissue separation method.According to morphological characteristics and ITS sequence analysis,strain HZ-MB13 was identified as Trametes hirsuta.It was found that the product of this strain withα-glucosidase inhibitory activity and antioxidant activity was exopolysaccharide.The single factor method was used to optimize the carbon and nitrogen source and the fermentation conditions of exopolysaccharide.As the result indicated,if 40 g/L fructose was taken as carbon source and 20 g/L corn syrup as nitrogen source,maximum yield of exopolysaccharide was(7.30±0.25)g/L in 125 mL medium volume in flask with initial pH of 5.5 at 150 r/min of rotating speed.Then,exopolysaccharide was extracted from the fermentation broth of strain HZ-MB13 by alcohol precipitation,and theα-glucosidase inhibitory activity and antioxidant activity were determined.The results showed that exopolysaccharide of strain HZ-MB13 had excellentα-glucosidase inhibitory activity whose IC50 value was 7.53 mg/mL,and good antioxidant activity and high scavenging activity for DPPH and ABTS free radicals.This study provides a theoretical basis for the production of diabetes drugs by fermentation of mulberry endophytic fungi.