Abstract

The type I polyketide geldanamycin is a potent anti-tumor reagent. Its biosynthesis includes three steps: the biosynthesis of precursors, such as 3-amino-5-hydroxybenzoic acid (AHBA), the polyketide synthase (PKS) chain extension, and the post-PKS modifications. According to the genomic and transcriptomic analysis, the PKS chain extension was deduced to be the rate-limiting step for geldanamycin production in Streptomyces hygroscopicus XM201. In order to improve the expression of PKS genes, a strong endogenous promoter 5063p was obtained based on the transcriptomic analysis and XylE enzymatic assay. By replacing the native PKS promoter gdmA1p with 5063p , the expression of the PKS genes during geldanamycin fermentation was increased by 4–141-folds, and the geldanamycin yield was increased by 39%. Interestingly, AHBA feeding experiment showed that the supply of AHBA in turn become a new rate-limiting factor for geldanamycin production. Further combined overexpression of the 6-gene AHBA biosynthetic cassette and PKS genes increased the yield of geldanamycin by 88%, from 773 mg L −1 of the wild-type to 1450 mg L −1 in the derived strain. Our results suggested that improved expression of all PKS genes in a particular biosynthetic gene cluster is important for the yield increase of the corresponding polyketide natural product. Graphical Geldanamycin is a strong antitumor reagent. In this study, the polyketide synthase (PKS) chain extension step in geldanamycin biosynthesis is speculated to be the rate-limiting step and is relieved by in situ overexpressing the 40 kb PKS genes, with a strong screened endogenous promoter. This work suggests that improved expression of all PKS genes in a particular biosynthetic gene cluster is important for the yield increase of the corresponding polyketide natural product.