Phylogenetic Analysis Of A Novel Natamycin-Producing Strain L10 And Construction Of Its Genetic Engineered Strain For Enhanced Natamycin Production

A novel Streptomyces strain,L10,which is capable of producing natamycin, was isolated from a soil sample collected from Zhejiang province,PR China.On the basis of phylogenetic analyses of rpoB gene and 16S rRNA gene sequences,as well as phenotypic comparison,strain L10 is coincidentally similar to the type culture of Streptomyces chattanoogensis in many properties but is distinguishable from the latter in respect of particular features including spore chain morphology,the ability of milk peptonization and getalin liquefaction,as well as the ability to utilize raffinose as sole carbon source.Thus,It appears reasonable to deduce that the L10 strain is a new strain of the known species Streptomyces chattanoogensis.Accordingly,the L10 strain is designated as Streptomyces chattanoogensis L10.The genomic library of Streptomyces chattanoogensis L10 was constructed in double cos site cosmid pHAQ31.By Cosmid library screening and primer walking, the sequences of most part of ScNRâ… gene and the whole ScNRâ…¡gene were obtained, as orthologues of natamycin positive regulators of Streptomyces natalensis. S.chattanoogensis D1,generated by inserting an additional copy of ScNRâ…¡into the chromosome of strain L10,reached a natamycin yield of 2.41g/l,about 3.3 fold than that of strain L10.Similar manipulation was also performed on an industrial natamycin-producing strain,the natamycin production of the genetic engineering strain reached 5.7g/l,about 1.22 fold than that of original strain.