Abstract：
As the only essential amino acid containing elemental sulphur, L-methionine has important physiological and biochemical functions in living organisms. However, the fermentative production of L-methionine has not met the requirements of industrial production because of its low production level. In this paper, the fermentation process of an efficient L-methionine producing strain E. coli W3110ΔIJAHFEBC trc-fliY trc-malY/PAM glyA-22 metF constructed previously was systematically optimized. Based on the optimal initial glucose concentration, the effects of different fed-batch fermentation processes, including DO-Stat, pH-Stat, controlling residual sugar control at different level and feeding glucose with constant rate, on L-methionine fermentation were studied. It was found that the control of glucose concentration greatly affected the fermentation process. Subsequently, an optimal fed-batch fermentation process was developed, where the L-methionine titer was increased to 31.71 g/L, the highest yield reported to date, while the fermentation time was shortened to 68 h. Meanwhile, a fermentation kinetics model under the optimal fed-batch fermentation conditions was established, which fitted well with the biosynthesis process of L-methionine. This study may facilitate further development of the fermentative production of L-methionine.
摘要：
作为唯一含有元素硫的必需氨基酸，L-蛋氨酸在生物体内具有重要的生理生化功能。然而,发酵生产L-蛋氨酸的生产水平较低,已不能满足工业生产的要求。在本文中,系统优化了先前构建的高效L-蛋氨酸生产菌株大肠杆菌W3110ΔIJAHFEBCtrc-flytrc-malY/PAMglyA-22metF的发酵过程。基于最佳的初始葡萄糖浓度,不同补料分批发酵工艺的影响，包括DO-Stat,pH-Stat,控制不同水平的残余糖控制和恒定速率的葡萄糖喂养，对L-蛋氨酸发酵进行了研究。发现葡萄糖浓度的控制极大地影响了发酵过程。随后，开发了一种最佳的补料分批发酵工艺，其中L-蛋氨酸滴度增加到31.71g/L，迄今为止报道的最高产量，发酵时间缩短至68h。同时，建立了最佳补料分批发酵条件下的发酵动力学模型,这与L-蛋氨酸的生物合成过程非常吻合。这项研究可能有助于L-蛋氨酸发酵生产的进一步发展。
