Improving the production of natamycin in Streptomyces natalensis HW-2 by L-valine feeding

L-valine (L-Val) was previously confirmed to promote natamycin biosynthesis in S. natalensis HW-2. In this study, natamycin yield was 1.9-fold increase with 0.5 g/L L-Val feeding. The level of free amino acids in the broth was significantly affected. Transcriptome analysis showed that 646 and 189 genes were significantly differential expression at 48 h and 60 h, respectively. 7 differential expression genes in branched-chain amino acids (BCAAs) degradation were up-regulated. To further investigate the role of BCAAs degradation on natamycin biosynthesis, the gene ilvE, which encoded branched-chain amino acid aminotransferase (BCAT), was homologously overexpressed. The optimal mutant, S. natalensis LY08, was obtained, and its natamycin production was increased by 179%. With the optimized L-Val supplementation concentration, natamycin yield was increased to 2.02 g/L by strain LY08. This finding indicated the roles of BCAAs degradation on natamycin biosynthesis, and provided an efficient strategy to improve natamycin production in S. natalensis.