Construction Of High-yield Candicidin Producing Strain

Candicidin, an antifungal heptaene macrolide compound, is produced by Streptomyces sp. FR-008 or Streptomyces griseus IMRU3570. The original strain ZYJ-6, a mutant of Streptomyces sp. FR-008, had been introduced into a global positive regulator adpAc gene,an S-adenosylmethionine synthetase gene (metK),a vgb gene encoding Vitreoscilla hemoglobin (VHb) and disrupted a global negative regulator nsdA gene, to investigate the relationship of each gene with candicidin biosynthesis.The results indicated that overexpression of adpAc and metK gene in ZYJ-6 showed a 10% and 40% increase in the candicidin productivity, respectively. Expression of Vitreoscilla hemoglobin enhanced growth and showed a 30% increase in the candicidin productivity. Disruption of nsdAF in Streptomyces sp. FR-008 had no effect on candicidin biosynthesis. Further research was to analyse the effect of two integral gene on candicidin productivity, they were both showed a 40% increase in the candicidin productivity when metK,vgb integral gene or metK,adpA integral gene was expressed in ZYJ-6, respectively. So we constructed an expression vector of metK,vgb,adpA integral gene. And we adopted the"Ribosome Engineering"method of streptomycin-resistant,gentamicin-resistant,rifamycin-resistant mutational screening of high-yield candicidin strain, acquired a streptomycin-resistant mutant STR-4 which showed a 40% increase in the candicidin productivity. Finally we acquired a high-yield candicidin producing strain , there was a 110% increase in the candicidin productivity when overexpression of metK,vgb,adpA integral gene in STR-4. It has a distinctive significance of constructing a general host for antibiotic production.