以1株由青藏高原牦牛粪中分离出的链霉菌为出发菌株,该菌株在发酵培养基中能产生胞外木聚糖酶(3 227.346 U/mL)。以此菌株为出发菌株,对其进行重离子辐照诱变处理,从大量突变株中筛选出木聚糖酶高产菌株SZ10-7,其酶活力达到5 338.42 U/mL,与出发菌株相比较,突变株SZ10-7的酶活力提高了1.65倍。对突变株SZ10-7的发酵条件进行了优化研究,结果表明,该菌株的木聚糖酶活力得到进一步提高,达到5 850.20U/mL,其最适发酵条件为:培养基(g/100 mL)为玉米芯∶麸皮(体积比1∶1)5,酵母膏0.8,K2 HPO4.3H2 O 0.1,MgSO4.7H20 0.5,NaCl 0.3,pH 7.0,培养温度25℃振荡培养时间96 h,实验结果表明,重离子辐照诱变技术是一种有效的微生物诱变育种新技术。

The growth property of Streptomyces sp.,a xylanase producing strain,isolated from the yak dung in Qinghai-Tibet plateau and the nature of xylanase were studied in this paper.Growing in fermentative medium,the strain can produce xylanase(3227.346U/mL).We delt with the original strain by the heavy-ion irradiation.We screened a high-yield xylanase producing strain SZ10-7 from many of mutants and its enzyme activity reached to 5 338.42 U/mL.Compared with the original strain,the enzyme activity of mutant strain SZ10-7 increased by 1.65 times.The fermentation conditions of the mutant strain SZ10-7 were optimized and its enzyme activity further increased,reaching to 5850.20 U/mL.The mutant's optimum conditions for enzyme production consisted of 5% the mixture of the corn cobs and the wheat bran(1∶ 1),0.8% yeast extract,0.1% K2HPO4·3H2O,0.5% MgSO4·7H20,0.3% NaCl,the initial pH 7.0,shaking culture for 96h,at 25℃.These results showed that the heavy-ion irradiation is an effective method for microbe mutagenesis.