Abstract: Succinic acid is considered to be one of the most promising bulk chemicals produced by white biotechnology and has a wide range of applications in industry. Microbial production of succinic acid has the advantages of environmental friendliness, and sustainable development, showing a good development prospect. However, a few issues remain with microbial production of succinic acid, such as the low yield, by-products accumulation and low productivity. In order to achieve the efficient production of succinic acid by Escherichia coli (E. coli) FMME-N-26, the fermentation conditions and feeding strategy were optimized in a 3.6 L fermenter. The process involved a two-stage fermentation, with aerobic cell growth followed by anaerobic conditions for succinic acid production. The optimal fermentation conditions were as follows: aerobic fermentation was transitted to anaerobic fermentation at 8 h, MgCO3 was used as pH neutralizer, 2 mmol/L betaine was added as osmoprotectants at 72 h, and glucose concentration was controlled to be 1~5 g/L in the anaerobic stage. The yield of succinic acid and the yield of glucose in anaerobic phase reached 119.2 g/L and 1.08 g/g (97% of the theoretical yield) at 72 h after optimized fermentation, which were 46.4% and 4.8% higher than those of the original fermentation, respectively. Only 2.37 g/L and 0.94 g/L of acetic acid, and lactic acid were accumulated as by-products, which were 37.1% and 49.2% lower than those of the before optimized fermentation, respectively. Then the scale-up production was realized in a 1000 L fermentation tank. The production of succinic acid yield, glucose yield and production intensity by E. coli FMME-N-26 were leading level at home and abroad. Taken together, this study provides a solid foundation for the industrial production of succinic acid and the strategies described here also pave the way to the production of other value-added chemicals.

Key words: Succinic acid, Escherichia coli, fermentation optimization, osmotic pressure, pH neutralizer

摘要： 琥珀酸(Succinic acid)被认为是白色生物技术生产的最具潜力的大宗化学品之一，在工业上具有广泛的应用。微生物发酵生产琥珀酸具有环境友好和可持续发展等优点，展现出良好的发展前景，但是存在得率低、副产物积累、生产强度低等问题。为了实现琥珀酸的高效生产，在3.6 L发酵罐中对E. coli FMME-N-26生产琥珀酸发酵条件和补料策略进行了优化，建立了好氧-厌氧两阶段发酵工艺，最终确定发酵策略为：有氧发酵8 h后转为厌氧发酵，MgCO3为pH中和剂，发酵72 h补加抗渗透压保护剂2 mmol/L甜菜碱，厌氧阶段控制葡萄糖浓度为1~5 g/L。优化后发酵72 h，琥珀酸的产量和厌氧阶段得率分别达到119.2 g/L和1.08 g/g葡萄糖(理论得率97%)，分别比优化前提高了46.4%和4.8%，副产物乙酸和乳酸仅积累2.37和0.94 g/L，分别比优化前降低了37.1%和49.2%。在1000 L发酵罐中实现中试放大生产，E. coli FMME-N-26生产琥珀酸的产量、得率和生产强度在国内外属于领先水平，为琥珀酸工业化生产奠定了坚实的基础，同时也为其他高价值化学品的生产提供了借鉴。

关键词: 琥珀酸, 大肠杆菌, 发酵优化, 渗透压, pH中和剂