蛹虫草原生质体紫外诱变选育胞外多糖高产菌株

蛹虫草是重要的药食兼用两用真菌，具有较高的医用及经济价值。本文通过单因素和正交试验的方法研究了不同酶系统、酶解温度、酶解时间、渗透压稳定剂、菌龄对蛹虫草原生质体形成的影响，并对蛹虫草原生质体进行紫外诱变，以生物量和胞外多糖产量为指标选育胞外多糖高产菌株。结果表明：在30℃、1％溶壁酶＋0．5％蜗牛酶＋0．5％纤维素酶条件下，以甘露醇为渗透压稳定剂对4日龄蛹虫草菌丝酶解2h，原生质体产量可达到9．2×10^6个/mL。从150株诱变株中筛选出1株最佳正诱变株，编号为44#，经深层培养其生物量比出发菌株提高10％，胞外多糖产量提高84．3％，继代培养10代后，遗传稳定性良好。

Mutagenesis of Cordyceps militaris protoplast for high production of exopolysaccharide

Cordyceps militaris is a valuable medicinal and edible fungus with high medical and economic value. The effects on the preparation conditions of protoplast from Cordyceps militaris, including enzymes, temperature and time of enzymolysis, stabilizing agent of osmotic pressure and the mycelium age of Cordyceps militaris were investigated by single-faetor and the orthogonal design. Protoplast from Cordyceps militaris was mutagenized with UV. The experiments results showed that the highest yield of protoplast could be obtained by using 1% lywallzyme ＋ 0.5 % snailase ＋ 0.5 % cellulose as cell wall digesting enzyme, mannitol as stabilizer of osmotic pressure, mycelittm of 4 days and enzyme treatment for 2 hours at 30℃. The production of protoplast reached 9.2 ×10^6/mE. Then mutant 44# was screened from 150 mutants with high exopolysaccharide yield and biomass. The biomass increased by 10% and exopolysaccharide yield increased by 84.3% compared with those of the original strain. After 10 generations, it still showed hereditary stability. The biomass and exopolysaeeharide yield of the mutant 44 # kept constantly.