Avermectin产生菌异亮氨酸诱导变种的选育

用紫外线处理ａｖｅｒｍｅｃｔｉｎ（ＡＶＭ）产生菌ＳｔｒｅｐｔｏｍｙｃｅｓａｖｅｒｍｉｔｉｌｉｓＸＣ１－２５，并在含有Ｌ－异亮氨酸（Ｌ－Ｉｌｅ）的平板培养基上筛选Ｌ－Ｉｌｅ诱导变种。结果表明：Ｉｌｅｉ变株发酵产生的ＡＶＭＢ１ａ效价高于自然分离株与紫外线诱变株，其中Ｉｌｅｉ变株ＸＣ２－２６的ＡＶＭＢ１ａ效价较亲株提高２２％。该变株经自然分离获得菌株ＸＣ３－８，其ＡＶＭＢ１ａ效价比出发菌株提高５０％以上，传代试验表明菌株ＸＣ３－８的形态和高产性能稳定，它在７ｍ３发酵罐生产试验，产生ＡＶＭＢ１ａ效价与发酵指数均比出发菌株提高５６％。

Selection of the isoleucine induced mutant strain of avermectin producing Streptomyces avermitilis

When the spore suspension of avermectin producing Streptomyces aver mitilis XC 1 25 was treated with UV. The isoleucine induced mutant strains which could grow on the agar medium containing 0.1% L isoleucine were isolated. The Ile i mutant produced more avermectin B la than the natural isolates and UV mutants. Among them the AVM B la potency of the Ile i mutant strain 2 26 was increased 22% more than that of the parent strain XC 1 25. The strain XC 3 8, whose AVM B 1a potency was increased by 26%, was isolated by natural selection of strain XC 2 26. Subculture test indicated that the heredity character of strain XC 3 8 was stable. The fermentation of strain XC 3 8 was performed in 7m 3 fermenter, and the AVM B 1a potency and index of fermentation increased by 56% was resulted.