Zhang Changqing, Gou Dongmei, Mei Jiajun, Liu Rongming, Ma Jiangfeng, Chen Kequan, Zhu Jianguo, Jiang Min
State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing University of Technology, Nanjing 211816, Jiangsu, China.
Sheng Wu Gong Cheng Xue Bao. 2012 Nov;28(11):1337-45.
Succinic acid production was inhibited by high osmotic pressure caused by the accumulation of sodium ions in the process of two-stage fermentation by Escherichia coli using Na2CO3 as the pH regulator. To enhance the resistance of this strain to osmotic stress, the possibility to isolate high NaCl-tolerant mutant strain of Escherichia coli for succinic acid production by metabolic evolution was investigated. The metabolic evolution system was used as a mutant-generating system, allowing the cells to be continuously cultured at the maximum specific growth rate. The mutant strain can grow at maximum rate in the condition of high osmotic by gradually improving the concentration of NaCl in a continuous culture. Then the high osmotic-tolerant mutant strain of E. coli XB4 was selected with NaCl as the osmo-regulator. When using Na2CO3 as the pH regulator, E. coli XB4 was used in a 7.0 L fermenter during two-stage fermentation. After 60 h anaerobic fermentation, the mutant strain XB4 produced 69.5 g/L succinic acid with a productivity of 1.18 g/(L x h), which were increased by 18.6% and 20% compared with that of the parent strain.
在以碳酸钠为pH调节剂的大肠杆菌两阶段发酵过程中，钠离子的积累导致高渗透压，从而抑制了琥珀酸的产生。为了增强该菌株对渗透胁迫的抗性，研究了通过代谢进化分离用于琥珀酸生产的高耐氯化钠大肠杆菌突变菌株的可能性。代谢进化系统用作突变产生系统，使细胞能够以最大比生长速率连续培养。通过在连续培养中逐渐提高氯化钠浓度，突变菌株能够在高渗透压条件下以最大速率生长。然后以氯化钠作为渗透压调节剂筛选出大肠杆菌高耐渗透突变菌株XB4。当使用碳酸钠作为pH调节剂时，在7.0 L发酵罐中对大肠杆菌XB4进行两阶段发酵。经过60小时厌氧发酵，突变菌株XB4产生了69.5 g/L琥珀酸，产率为1.18 g/(L·h)，与亲本菌株相比分别提高了18.6%和20%。
