Engineered Biosynthesis of Complex Disorazol Polyketides in a Streamlined Burkholderia thailandensis.

Engineering the biosynthetic pathways of complex natural products is a significant approach to obtain derivatives with improved properties. Here, we constructed a streamlined engineered biosynthesis system of myxobacterium-derived complex polyketide disorazol in a heterologous host, Burkholderia thailandensis E264. Inactivation of dehydratase domains in the disorazol biosynthetic pathway led to the production of two hydroxylated derivatives. Module deletion allowed the generation of an unnatural derivative with a truncated macrolactone ring, and the ACP-KS linker was the optimal fusion region for module deletion in this trans-AT polyketide synthase. These disorazol derivatives showed different activities against human cancer cell lines ranging from the nanomolar to micromolar level, suggesting the primary structure-activity relationship. The PKS engineering enables structural derivatization of disorazol, facilitating the in-depth engineered biosynthesis of polyketides.

Engineering of Burkholderia thailandensis strain E264 serves as a chassis for expression of complex specialized metabolites.

Heterologous expression is an indispensable approach to exploiting natural products from phylogenetically diverse microbial communities. In this study, we constructed a heterologous expression system based on strain Burkholderia thailandensis E264 by deleting efflux pump genes and screening constitutive strong promoters. The biosynthetic gene cluster (BGC) of disorazol from Sorangium cellulosum So ce12 was expressed successfully with this host, and the yield of its product, disorazol F2, rather than A1, was improved to 38.3 mg/L by promoter substitution and insertion. In addition to the disorazol gene cluster, the BGC of rhizoxin from Burkholderia rhizoxinica was also expressed efficiently, whereas no specific peak was detected when shuangdaolide BGC from Streptomyces sp. B59 was transformed into the host. This system provides another option to explore natural products from different phylogenetic taxa.