The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi, 214122, Jiangsu, China.
College of Life Sciences, Huaibei Normal University, Huaibei, 235000, Anhui, China.
Bioprocess Biosyst Eng. 2018 Aug;41(8):1143-1151. doi: 10.1007/s00449-018-1943-y. Epub 2018 Apr 21.
The glucose-glycerol mixed carbon source remarkably reduced the batch fermentation time of ε-poly-L-lysine (ε-PL) production, leading to higher productivity of both biomass and ε-PL, which was of great significance in industrial microbial fermentation. Our previous study confirmed the positive influence of fast cell growth on the ε-PL biosynthesis, while the direct influence of mixed carbon source on ε-PL production was still unknown. In this work, chemostat culture was employed to study the capacity of ε-PL biosynthesis in different carbon sources at a same dilution rate of 0.05 h. The results indicated that the mixed carbon source could enhance the ε-PL productivity besides the rapid cell growth. Analysis of key enzymes demonstrated that the activities of phosphoenolpyruvate carboxylase, citrate synthase, aspartokinase and ε-PL synthetase were all increased in chemostat culture with the mixed carbon source. In addition, the carbon fluxes were also improved in the mixed carbon source in terms of tricarboxylic acid cycle, anaplerotic and diaminopimelate pathway. Moreover, the mixed carbon source also accelerated the energy metabolism, leading to higher levels of energy charge and NADH/NAD ratio. The overall improvements of primary metabolism in chemostat culture with glucose-glycerol combination provided sufficient carbon skeletons and ATP for ε-PL biosynthesis. Therefore, the significantly higher ε-PL productivity in the mixed carbon source was a combined effect of both superior substrate group and rapid cell growth.
葡萄糖-甘油混合碳源显著缩短了 ε-聚赖氨酸（ε-PL）分批发酵时间，提高了生物量和 ε-PL 的生产效率，这在工业微生物发酵中具有重要意义。我们之前的研究证实了快速细胞生长对 ε-PL 生物合成的积极影响，而混合碳源对 ε-PL 生产的直接影响尚不清楚。在这项工作中，采用恒化器培养来研究在相同稀释率 0.05 h 下不同碳源对 ε-PL 生物合成的能力。结果表明，混合碳源除了促进快速细胞生长外，还可以提高 ε-PL 的生产力。关键酶分析表明，在恒化器培养中使用混合碳源时，磷酸烯醇丙酮酸羧激酶、柠檬酸合酶、天冬氨酸激酶和 ε-PL 合成酶的活性均增加。此外，在三羧酸循环、氨甲酰磷酸途径和二氨基庚二酸途径中，混合碳源也提高了碳通量。此外，混合碳源还加速了能量代谢，使能量电荷和 NADH/NAD 比值更高。恒化器培养中葡萄糖-甘油组合的初级代谢的整体改善为 ε-PL 生物合成提供了足够的碳骨架和 ATP。因此，混合碳源中 ε-PL 生产力的显著提高是优越的基质组和快速细胞生长的综合作用。
