Breeding of ε-poly-L-lysine producing strain with combined mutation and the optimization of its fermentation medium

Using Streptomyces albulus FQ-9 as the initial strain mutated by UV combined with Li Cl,and using glycine +sulfaguanidine(SG) +L-lysine as selective markers. Then,a ε-PL-producing strain,Streptomyces albulus FQC-23 of the yield improved to(0.668±0.0045) g/L was screened,which was 15.37% higher than that of FQ-9. Moreover,based on single factor experiment,the fermentation medium of ε-PL producing strain FQC-23 were optimized by response surface methodology,and finally determined the optimal fermentation medium as follows(g/L):glucose 46.1,yeast powder 13.0,(NH4)2SO45.9,Mg SO4·7H2O 0.5,K2HPO40.8,KH2PO41.36,Fe SO4·7H2O 0.03,Zn SO4·7H2O 0.04. Under the optimized medium,the yield of ε-PL reached(1.090±0.0041) g/L and increased by 87.56% compared with the previous condition.