为实现Streptomyces sp.M-Z18补料-分批发酵甘油生产ε-聚赖氨酸(ε-PL)的自动流加碳源和解决因发酵中后期菌体生长速率下降/停滞引起ε-PL合成速率下降的问题,该文首先借助DO-stat反馈补料方法,考察了补料阶段甘油控制在不同浓度范围内对ε-PL合成的影响;然后,通过在发酵中期分别流加牛肉膏和酵母粉,研究了2种有机氮源对发酵中后期菌体生长和ε-PL合成的影响;最后,在2阶段pH调控策略基础上,评价了上述最优控制条件下对Streptomyces sp.M-Z18合成ε-PL的促进作用。实验结果表明,依靠DO-stat反馈补料方式将补料阶段甘油浓度稳定控制在0~10 g/L,并在发酵96 h开始流加酵母粉和(NH4)2SO4混合液,结合pH值2阶段调控策略(3.5→3.8),经过192 h发酵,可以实现ε-PL产量达到38.77 g/L,产率达到4.85 g/(L·d)。基于碳源和氮源流加方式的优化,建立的DO-stat反馈流加甘油策略和提出的发酵中期流加酵母粉和(NH4)2SO4混合液的方法是提高ε-PL发酵水平的有效方法之一。

To develop an automated feeding strategy for ε-poly-L-lysine(ε-PL) production during fed-batch fermentation and resolve the problem of ε-PL synthesis rate decreased in the middle phase of fermentation derived from the decrease or cease of Streptomyces sp.M-Z18 cell growth,we have investigated DO-stat feeding glycerol approach and constant feeding different organic nitrogen sources during fermentation in this study.Based on the optimization of initial glycerol concentrations(60 g / L),different ranges of glycerol concentrations(0 ~ 2,0 ~ 10,0 ~ 20,0 ~ 30 g / L) have been achieved by DO-stat feeding strategy during fed-batch fermentation,and determined by 0 ~ 10 g / L as the optimal concentration for ε-PL production and cell growth by Streptomyces sp.M-Z18.The experiments of feeding beef and yeast extracts during fed-batch fermentation from 96 h showed that yeast extract had significantly enhanced by 28.7% in ε-PL production when pH was kept at 3.8.When DO-stat feeding glycerol approach and constant feeding yeast extract together with the two-stage pH control strategy(3.5→3.8) was simultaneously performed in ε-PL fedbatch fermentation by Streptomyces sp.M-Z18,ε-PL production and productivity were finally attained by 38.77 g / L and 4.85 g /(L·d),respectively,after 196 h fermentation.