过表达pls基因结合前体流加提高小白链霉菌ε-聚赖氨酸产量

Enhanced ε-poly-L-lysine production through overexpression of pls gene combined with precursor feeding in Stretomyces albulus

为了提高小白链霉菌(Streptomyces albulus)的ε-聚赖氨酸(ε-poly-L-lysine,ε-PL)发酵产量,以进一步降低其生产成本,该研究通过过表达ε-PL合成酶基因pls增强S. albulus合成ε-PL能力,并结合前体和能量辅因子流加强化其发酵过程。研究结果显示,过表达菌株S. albulus M-Z18/p IB139-pls的pls基因转录上调了16. 8倍,摇瓶ε-PL产量达到(2. 74±0. 23) g/L,5 L发酵罐ε-PL产量达到40. 62 g/L(144 h)。为进一步满足过表达菌株合成ε-PL过程中对前体和能量辅因子的需求,通过优化L-赖氨酸和ATP外源添加浓度,最终建立S. albulus M-Z18/p IB139-pls在5 L发酵罐中同时流加5. 0 g/L的L-赖氨酸和1. 0 mmol/L ATP的补料分批发酵方式,实现ε-PL产量达到45. 09 g/L(144 h),较对照菌株S. albulus M-Z18/p IB139提高了20. 8%。因此,采用过表达pls基因并结合补充前体L-赖氨酸和能量辅因子ATP是一种有效提高S. albulus的ε-PL发酵水平的策略,研究结果为提高生产菌的ε-PL发酵水平提供了参考。

To increase the production of ε-poly-L-lysine( ε-PL) of Streptomyces albulus and reduce its production cost further,overexpression of ε-PL synthetase gene pls in S. albulus combined with the addition of the precursor and energy co-factor during fermentation was employed in this study. The results showed that the pls gene transcription in S. albulus M-Z18/p IB139-pls was up-regulated by 16. 8-fold,and the ε-PL production in shake flask and 5 L fermenter reached( 2. 74 ± 0. 23) g/L and 40. 62 g/L( 144 h),respectively. In order to further meet the needs of the engineered strain for precursor and energy substances during the biosynthesis of ε-PL,the concentrations of L-lysine and ATP were optimized in shake-flask fermentation,and finally the fed-batch fermentation mode with the addition of5. 0 g/L L-lysine and 1. 0 mmol/L adenosine triphosphate( ATP) in a 5 L fermenter was developed.The production of ε-PL reached 45. 09 g/L( 144 h) and increased by 20. 8% than that of the control strain S. albulus M-Z18/p IB139. As a result,it is an effective strategy to improve ε-PL production of S. albulus by overexpression of pls gene and the addition of L-lysine and ATP during fermentation. The result provides a reference for improving ε-PL production.