Study On The Breeding Of Production Strains And Optimizing Fermentation Media Of Josamycin Producer JOS-20

A stable mutated strain was obtained from the spores of josamycin producer S.narbonensis var. josamyceticus JOS-20 by purification. The spores of JOS-20 were mutated by seven methods such as LiCl-UV, Streptomycin resistant rational screening , ~60Co-γ irradiation , protoplast regeneration , protoplast -UV, protoplast electroporation and nitrite .The result showed that all these methods could enhance the fermentation ability of strains , but the protoplast electroporation was the most effectual methods . Three strains (yx-36,yx-94,yx-245)were screened out after all the tests above. Subculture test indicated that yx-245 had relatively stable hereditary characteristics than others ,so it was considered the best strain and would be used in the fermentation media optimized experiment.the fermentation media optimized experiment with yx-245 was on shaking flask level. Based on primary media, the effect of all components in the primary media to producing josamycin were investigated. And orthogonal experiments of every component of the fermentation media were managed to screen out the fermentation media . As a result ,a preferable fermentation medium was found. And the chemical titer of the yx-245 in the new fermentation media were increased by 17.76% compared with its in the old one .