小白链霉菌全细胞转化L-赖氨酸合成ε-聚赖氨酸的体系构建与优化OACSTPCD

Streptomyces albulus is the main producer of ε-poly-L-lysine(ε-PL).ε-PL is a natural antimicrobial peptide used primari-ly as a biological preservative in food industry,but its widespread application is limited by its high costs.To improve the production effi-ciency of S.albulus,this study used a whole-cell transformation method to produce ε-PL.Firstly,the synthesis efficiency of ε-PL in dif-ferent fermentation systems was compared,and the whole-cell transformation system was found to produce the highest ε-PL yield,reaching 10.74 g/L.Then,the transformation medium and conditions were systematically optimized,and the optimal transformation conditions was obtained:glucose 80 g/L,cell culture time 12 h,reaction temperature 30 ℃,L-lysine 15 g/L,citric acid 15 g/L,initial pH 4.0,(NH4)2SO4 6 g/L,and wet biomass 1 900 g/L.In the optimal system,the ε-PL yield and substrate conversion rate reached 13.80 g/L and 38.9％,respectively,which were 4.1 and 3.2 folds higher than those in shake flask fermentation system.Finally,the L-lysine spe-cific permease gene(lysp)from Escherichia coli BL21 was heterologous expressed to enhance the strain's ability to uptake exogenous L-ly-sine.Compared with the starting strain,the recombinant strain S.albulus OE-lysp showed a 26％increase in L-lysine utilization rate and a 33％increase in substrate conversion rate.The ε-PL yield also increased by 17.21 g/L,about 6.4 times higher than that in shake flask fermentation system,which is to our knowledge the highest reported ε-PL production in shake flask fermentation system.The results dem-onstrate the feasibility of producing ε-PL using a whole-cell transformation method and provide a solid technical foundation for the produc-tion of high-value ε-PL using L-lysine.Therefore,this study has important theoretical significance and high economic value.