Breeding Of Jinggangmycin-producing Strain By N~+Implantation And Optimization On Fermentation Conditions

Jinggangmycin has been well known as an antibiotic fermented by Streptomyces hygroscopicus var. jinggangsis yen. It can effectively control rice sheath blight caused by Rhizoctonia solani. It’s a low cost, high effective and safty agricultural antibiotic which is the largest one in production and application scale. Jinggangmycin A(VAL-A) has been applied for nearly40years without becoming resisted in antibiotic use; it still has a stable market. Low energy ion beam implantation was used in this work to mutate Streptomyces hygroscopicus var. jinggangsis yen. The effective component VAL-A high-yield mutative strain with high genetic stability was obtained. The optimization of fermentation medium for VAL-A high-yield strain obtained from mutation was carried out simultaneously.First low energy ions beam implantation was used to mutate the original strain. As one classical mutation method for antibiotic-producing strains, the optimal mutagenic dose80X2.6X1013ion/cm2was confirmed by reviewing6dose, energy l0kev mutagenic effectiveness. The positive mutation rate was as high as71.4%, and the amplitude is up to30.3%. After multi-cycle breeding, Streptomyces hygroscopicus var. jinggangsisyen has a higher death rate and positive mutation rate. The results indicate that effective component VAL-A of mutative strain SHJ381implanted with mutagenesis was13%higher, up to25.4g/L, than original strain, and with high genetic stability.The high-yielding strain characteristics changed after mutagenesis. The fermentation culture medium was optimized by orthogonal designed single factor experiment. The optimal culture medium for fermentation were shown as follows:rice flour8%, amylum0.7%, soybean meal1%, yeast flour1%, KH2PO40.12%, NaCl0.15%, CaCO30.2%, corn flourl.4%. On the same conditions, it was found that the optimal medium which was helpful to increase the yields of the VAL-A by38%(from24.8to34.5g/L) than the original medium.As a result, the combined effects of high producing mutant and optimal medium could significantly increase the VAL-A production by about56%.Determination of the optimal medium for high-yield strains of VAL-A yield curve, the assay showed that overproducing strain to stabilize the fermentation broth of VAL-A content in the basic no longer have a greater change in96hour. Therefore,96th hour can be used as the end of fermentation time.