Selection of Streptomyces roseosporus strain with high yield by the inactivated parental strain protoplasts fusion

[Objective] To select the daptomycin-producing strain with high yield. [Method] The protoplast of Streptomyces roseosporus SDDT57 was killed by ultraviolet (Wavelength 253 nm, irradiation distance 30 cm) for 8 min, and that of Streptomyces roseosporus SUDT57 was killed by heating (75t) for 60 min. Then both the killed protoplasts were fused in PEG. The strain with high yield was isolated from the fused protoplasts. [Result] The strain with the highest yield was named S. roseosporus SF06. The Shake flask fermentation was performed with capric acid. The production was improved to 113.74 mg/L, which was 2.46 and 2.47 times that of the two original strains respectively. [Conclusion] It is viable to select daptomycin producing strain with high yield by the inactivated parental strain protoplasts fusion. This study provides much for the next research on Genome shuffling of Streptomyces roseosporus.