| Zhongshengmycin, which was produced by Streptomyces lavendulue Var. Hainanensis is a type of N-glycoside agricultural antibiotics. It has wonderful effect on preventing and treating bacterial diseases and some fugal diseases of crops and vegetables.In order to obtain higher Zhongshengmycin-producing strains, different breeding methods were used to treat Streptomyces lavendulue Var. Hainanensis. High-production mutants UV-69 and E-25 were obtained from parent strain C5 and 6937 was obtained from parent strain UV-69. The good inhibitory effect of Zhongshengmycin on both bacterial and fungi was considered as potency index, using mutative breeding. The orthogonal design method was adopted to select the optimum growth and fermentation medium for original strain C5. The methods of strain improving was described in detail.1. Streptomyces lavendulue Var. Hainanensis C5 as a starting strain was treated compositely by spore sprouting and ultraviolet irradiation to improve Zhongshengmycin production . Results indicated that the optimum time of spore spouting is 3 hours before UV treatment. Compared with other treatments, the rate of positive mutants and the rate of mutation increased . We obtained a high-production mutants UV-69 and its fermentation titer was 3700ug/ml in shaking flasks, which was 41.32% higher than that of the starting strain C5. Subculture test indicated that the hereditary character of strain UV-69 was stable. In an 20-ton fermentation tank, the average potency of five successive batches was 4370(j,g/ml, which was 45.60% higher than the existing production level. It was proved that strain UV-69 is a high and stable producing strain for industrialproduction.2. Starting strain C5 was treated by high electron beam implanting and ultraviolet irradiation compound mutation breeding to improve Zhongsheng-mycin production. Results indicated that in comparison with high energy electron beam implanting, compound mutation have the higher rate of positive mutants and the relative higher titer. A mutant E-25, whose productivity was superior to parent strain was selected. Its fermentation titer was 4075 jag/ml in shaking flasks, which was 53.78% higher than that of the starting strain C5. The mutation effect of high energy electron beam implanting 5 seconds and ultraviolet irradiation 15 seconds compound mutation breeding was better than that of high energy electron beam implanting 15 seconds and ultraviolet irradiation 15 seconds compound mutation breeding.3. High-yield strain UV-69 as a starting strain was treated by ultraviolet irradiation and AEC compound mutation to improve Zhongshengmycin yield. The experiment showed that with the growth of AEC content, the rate of positive mutants increased. When AEC tolerant concentration was 10p,g/ml , the rate of positive mutants was the highest , which was 11.59%. Two high-producing mutants A-23 and A-02 were obtained whose fermentation titer were about 4400^g/ml in shaker flasks. By ultraviolet irradiation, two good mutants 6937 and 6904 were obtained whose fermentation titer in shaker were over 4500 jag/ml. Subculture test indicated that the hereditary character of strain 6937 was stable, but other three mutants 6904, A-23 and A-02 which possessed the capacity for higher production of Zhongshengmycin were almost at the same level as the original strain UV-69.4. High-yield strain UV-69 as a starting strain was treated by ultraviolet irradiation and streptomycin compound mutation to improve Zhongsheng-mycin production. It had been found that there was the relation between the biosynthesis of Streptomyces antibiotics and the streptomycin-resistance . So the production of Streptomyces antibiotics was probably improved when the streptomycin-resistance increased . Results showed that the mutative effect of ultraviolet46irradiation and streptomycin compound mutative breeding was better than that of ultraviolet irradiation. The ratio of forward mutative strains was 11.32% when streptomycin concentration was 2p,g/ml and was higher...
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