Combinatorial metabolic engineering strategy of precursor pools for the yield improvement of spinosad in Saccharopolyspora spinosa.

Spinosad is an insecticide produced by Saccharopolyspora spinosa, and its larvicidal activity is considered a promising approach to combat crop pests. The aim of this study was to enhance the synthesis of spinosad through increasing the supply of acyl-CoAs precursor by the following steps. (i) Engineering the β-oxidation pathway by overexpressing key genes within the pathway to promote the synthesis of spinosad. The results showed that the overexpression of fadD, fadE, and fadA1 genes, as well as the co-expression of fadA1 and fadE genes, increased the yield of spinosad by 0.36-fold, 0.89-fold, 0.75-fold and 1.25-fold respectively. (ii) Employing combinatorial engineering of the β-oxidation pathway and ACC/PCC pathway to promote the synthesis of spinosad. The results showed that the co-expression of fadE and pccA, as well as accC and fadE, resulted in a 1.77-fold and 1.43-fold increase in spinosad production respectively. (iii) When exogenous triacylglycerol was added to the fermentation medium, the solely engineering of the β-oxidation pathway increased the yield of spinosad by 7.13-fold, reaching 427.23 mg/L. While the combinatorial engineering of both the β-oxidation pathway and ACC/PCC pathway increased the yield of spinosad by 9.61-fold, reaching 625.17 mg/L, and further optimization of the culture medium resulted in an even higher yield of spinosad, reaching 1293.43 mg/L. The results of this study indicate that the above combination strategy can promote the efficient biosynthesis of spinosad.