The Studies On Strain-improving For Streptomyces Avermitilis

In this paper, Streptomyces avermitlis was used as experimental object, the original strain AV20 was treated by chemical mutagen. First, the strain, was treated by NTG, DES, then the methionine induction model and methylamine tolerance model were used as screening models to select strains, as a result, a favorable strain DMa-46 was obtained, its B1a components was about 43.2%.Then, HNO₂ was used as mutagen to treat the strain DMa-46, and selected strains by the streptomycin tolerance model. After screening, a strain H₂S10-13 was obtained, its percentage of B component was 15% higher than the original strain, its total fermentation titer was 1986μg/mL more than the original strain.In the course of strain screening, two mutant, H₁20-40 and H₃20-12 were obtained. Investigation of metabolites accumulated by the strains showed that: the main metabolites of H₁20-40 was oligomycin A, the percentige of oligomycin A reached to about 85%, and the fermentation titer of oligomycin A reached 733μg/mL. H₃20-12 produced only two main components, ZL and B2a.. The percentage of ZL was about 42%, the fermentation titer of ZL was 762μg/mL; while the percentage of B2a was about 40.6%,the fermentation titer of B2a was 732 the total fermentation titer of H₃20-12 was 1989μg/mL.