Construction Of The High Natamycin-Producing Strains And Optimization On Their Fermentation Conditions

Natamycin,as one kind of polyene macrolide antibiotics,is a broad-spectrum antifungal agent.It is widely used in food industries and medical treatment. However,the application of natamycin is limited because of the low yield of natamycin and the high cost of production.Therefore,it's of great significance to improve the natamycin production by genetic engineering.By Southern blotting and primer walking,the sequence of scnRâ… gene was obtained from the cosmid pMRD46,as a orthologue of natamycin pathway-specific positive regulator gene in Streptomyces chattanoogensis.scnRâ…¡is another pathway-specific positive regulator gene obtained by our laboratory previously.The DNA fragments of scnRâ… +Np(with its own promoter),scnRâ…¡+ermE~*P,scnRâ… +scnRâ…¡+Np(with theri own promoters) were ligated with pIJ8630,respectively,resulting in plasmid pLY2,pLY4,pLY5,which were then transferred into the original natamycin-producing strain S.chattanoogensis by conjugation respectively,generating genetic engineered strains S.chattanoogensis ZJUC1,ZJUC2,ZJUC3.In YEME medium without sucrose,ZJUC1,ZJUC2,ZJUC3 reached the natamycin yield of 1.96g/L,1.91g/L,2.12g/L respectively,about 1.17,1.14,1.27 fold than that of the starting strain.ZJUC3 reached a natamycin yield of 3.76 g/L in YSG medium,which was 1.33 fold of the starting strain.The orthogonal design optimized the YSG medium and the optimized cultivation conditions were as follows:glucose 60g/L,soybean meal 27 g/L,yeast meal 6.5 g/L,pH8.The optimized YSG medium rendered the natamycin production of ZJUC3 to be increasd from 3.76 g/L to 4.14g/L.