1 A Novel Strategy for Heterologous Production of the 2 Depsipeptide Ionophore Valinomycin 3

Streptomyces genome analyses have revealed an enormous abundance of gene clusters 12 codifying enzymes from secondary metabolism inferring that their potential to produce metabolites 13 is underestimated. Among the mostly useful natural products, those biosynthesized by 14 nonribosomal peptides synthetases share both high molecular complexity and therapeutic activity. 15 A gene cluster encoding the biosynthesis of valinomycin, a depsipeptide ionophore, was annotated 16 from the whole genome sequencing of the endophytic strain Streptomyces sp. CBMAI 2042 isolated 17 from Citrus ssp. In the present study, we describe the association of fermentation process, molecular 18 networking and mass spectrometry imaging which revealed the production of the ionophore by the 19 endophytic strain. Additionally, the heterologous expression of the entire valinomycin gene cluster 20 in S. coelicolor M1146 host was successfully promoted, representing an alternative and unique 21 platform for production of new valinomycin derivatives in future studies. 22