Mutagenesis and strain-improving of avermectin-producing strain Streptomyces avermitilis

Objective To increase avermectin B 1a yield of Streptomyces avermitilis.Method NTG was used as mutagen in treating avermectin-producing strain and medium containing 0.1% methionine was used as separation plate medium to select strains growing fast on such plate.Results Strains of high-yield avermectin B were obtained,among them strain M—20 was confirmed being a stable high-yield avermectin B producer,which produced 82.1% avermectin B,14.6% higher than original strain,and B 1a content reached 52.4%,19.3% higher than original strain.Conclusion It is a effective way to obtain high-yield avermectin B 1a producer by using NTG as mutagen and using separation plate medium containing 0.1% methionine to select strains.