Avilamycin production enhancement by mutagenesis and fermentation optimization in Streptomyces viridochromogenes.

Avilamycin, an excellent growth-promoting feed additive, produced by Streptomyces viridochromogenes, was widely used to promote the growth of poultry by inhibiting Gram-positive bacteria. In this work, the methods of combinational mutagenesis of UV (Ultraviolet) and ARTP (Atmospheric and room temperature plasma), and rational screening by high concentrations of CaCl2 were utilized to promote the production of avilamycin. The avilamycin high-yielding mutant strains of Z-6 (29.31 mg/L), A-9 (36.84 mg/L) and F-23 (45.73 mg/L) were screened out, with yields of avilamycin improved by 57.92%, 98.49% and 146.39%, respectively, compared with the wild strain (WT). The performance comparison showed that Z-6, A-9 and F-23 mutant strains had stronger abilities of substrate consumption, cell growth and antibiotic synthesis than WT. Furthermore, the composition of fermentation medium, inoculation parameters, supplementation strategies of oxygen vectors, glucose and precursors (L-valine, D-xylose and sodium acetate) had been optimized and the avilamycin yield of the mutant strain F-23 was significantly enhanced by 41.87% by fermentation optimization. In summary, the strategy of increasing the production of avilamycin in S. viridochromogenes in this work might provide an alternative method to enhance the synthesis of secondary metabolites in other Streptomyces.