Abstract:[Objective] To enhance the production of enramycin by Streptomyces fungicidicus. [Methods] In this study, the ribosomal S12 protein encoding gene rpsL which affects the secondary metabolism and biosynthesis of antibiotics in enramycin producing strain of S. fungicidicus F1 was changed through the method of site-directed mutation, during which the Lys43 was substituted for Asn and Arg, respectively. And then the growth characteristics, synthesis of antibiotic and flask fermentation performance of the modified strains were studied. [Results] The results showed that the growth characteristics and physiological and biochemical characteristics of the modified strains were significantly changed compared with the wild type strain. Sporulation cycle was shorten, spore was produced from wild type strain using MS medium under the condition of 28 °C for 5?7 days, but the modified strains can produced large amounts of spore only after 3 days in the same conditions. Enramycin yield was relatively increased. Under the flask formation condition, the enramycin production of the modified strains of L-M1(Asn43) and L-M2(Arg43) can reach a maximum of 1 334 U/ml and 1 456 U/mL, respectively. Compared with the wild-type strain, it was improved by 11.9% and 22.1% separately. [Conclusion] Through the genetic modification, the yield of enramycin was improved, which might provide a feasibility for the modification of other sites.
