Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, Jiangnan University, Wuxi 214122, China.
J Biotechnol. 2013 Aug 10;167(1):56-63. doi: 10.1016/j.jbiotec.2013.06.008. Epub 2013 Jun 20.
In previous work, three evolved Propionibacterium acidipropionici mutants with higher tolerant capacity of propionic acid (PA) were obtained by genome shuffling. Here, we attempted to unravel the acid-tolerant mechanism of P. acidipropionici by comparing the physiological changes between P. acidipropionici and three mutants. The parameters used for comparison included intracellular pH (pHi), NAD⁺/NADH ratio, H⁺-ATPase activity, and the intracellular amino acids concentrations. It was indicated that the acid tolerance of P. acidipropionici was systematically regulated. Specifically, low pHi promoted the P. acidipropionici to biosynthesize more H⁺-ATPase to pump the protons out of the cells, and as a result, the NAD⁺/NADH ratio increased due to the decreased protons concentration. The increased arginine, aspartic acid, and glutamic acid concentrations helped to resist the acidic environment by consuming more H⁺ and generating more ATP and NH₃. Based on what was analyzed above, 20 mM arginine and aspartic acid were added during the shaker culture of P. acidipropionici, and the maximal PA titer reached 14.38 g/L, which was increased by 39.9% compared with the control.
在之前的工作中，通过基因组重排获得了三株具有更高丙酸耐受能力的进化丙酸丙酸杆菌突变体。在这里，我们试图通过比较丙酸丙酸杆菌和三种突变体之间的生理变化来揭示丙酸丙酸杆菌的耐酸机制。用于比较的参数包括细胞内 pH 值（pHi）、NAD⁺/NADH 比、H⁺-ATP 酶活性和细胞内氨基酸浓度。结果表明，丙酸丙酸杆菌的耐酸性受到系统调节。具体来说，低 pHi 促使丙酸丙酸杆菌合成更多的 H⁺-ATP 酶将质子泵出细胞，结果由于质子浓度降低，NAD⁺/NADH 比增加。增加的精氨酸、天冬氨酸和谷氨酸浓度通过消耗更多的 H⁺和产生更多的 ATP 和 NH₃ 来帮助抵抗酸性环境。基于以上分析，在丙酸丙酸杆菌的摇瓶培养过程中添加了 20mM 的精氨酸和天冬氨酸，丙酸的最高产量达到 14.38g/L，与对照相比提高了 39.9%。
