Salinomycin biosynthesis reversely regulates the β‐oxidation pathway in Streptomyces albus by carrying a 3‐hydroxyacyl‐CoA dehydrogenase gene in its biosynthetic gene cluster

Streptomyces is well known for synthesis of many biologically active secondary metabolites, such as polyketides and non‐ribosomal peptides. Understanding the coupling mechanisms of primary and secondary metabolism can help develop strategies to improve secondary metabolite production in Streptomyces. In this work, Streptomyces albus ZD11, an oil‐preferring industrial Streptomyces strain, was proved to have a remarkable capability to generate abundant acyl‐CoA precursors for salinomycin biosynthesis with the aid of its enhanced β‐oxidation pathway. It was found that the salinomycin biosynthetic gene cluster contains a predicted 3‐hydroxyacyl‐CoA dehydrogenase (FadB3), which is the third enzyme of β‐oxidation cycle. Deletion of fadB3 significantly reduced the production of salinomycin. A variety of experimental evidences showed that FadB3 was mainly involved in the β‐oxidation pathway rather than ethylmalonyl‐CoA biosynthesis and played a very important role in regulating the rate of β‐oxidation in S. albus ZD11. Our findings elucidate an interesting coupling mechanism by which a PKS biosynthetic gene cluster could regulate the β‐oxidation pathway by carrying β‐oxidation genes, enabling Streptomyces to efficiently synthesize target polyketides and economically utilize environmental nutrients.