Improvement of daptomycin production via increased resistance to decanoic acid in Streptomyces roseosporus.

Daptomycin, a cyclic anionic lipopeptide compound produced by Streptomyces roseosporus, is used to treat skin infections caused by multi-drug resistant gram-positive pathogens. The biosynthesis of daptomycin is initiated by the condensation of decanoic acid (DA, a 10-carbon unit fatty acid) and the N-terminal l-tryptophan. So, the addition of DA to the fermentation medium is essential for increasing daptomycin production. However, increasing of DA concentration in the fermentation medium was not possible due to the high toxicity of DA. The previous studies reported that the cell growth of S. roseosporus was halted from 1 mM DA. In order to improve daptomycin production with increasing DA concentration in the medium, the DA-resistant S. roseosporus was developed via a sequential-adaptation method. The DA-resistant strain (DAR) showed complete resistance to 1 mM DA, and the daptomycin production was increased 1.4-fold (40.5 ± 0.7 mg/L) compared with the wild-type (28.5 ± 0.8 mg/L) at 1 mM DA. Additionally, the initial step of the daptomycin biosynthesis was enhanced by the overexpression of dptE and dptF in DAR. The dptEF overexpression DAR showed 3.9-fold (156.3 ± 8.2 mg/L) increase in the daptomycin production compared with DAR (40.1 ± 2.6 mg/L) at 1 mM DA.