粘质沙雷氏菌发酵生产D-乳酸的研究

Production of D-lactic acid by Serratia marcescens

本文对粘质沙雷氏菌发酵生产D-乳酸进行了研究。以粘质沙雷氏菌G1(Serratia marcescens G1)为出发菌种,摇瓶试验确定了发酵培养方式:前12 h为菌体生长阶段,有氧培养,温度28℃,pH值7.0;后36 h为D-乳酸合成积累阶段,无氧培养,温度44℃,pH值6.0。且发现使用葡萄糖为碳源时更有利于D-乳酸的合成积累。采用缺失2,3-丁二醇合成能力的基因工程菌株R1为出发株,经筛选后得到耐受较高浓度乳酸盐的菌株R150,以R150为发酵菌种,在3.7 L发酵罐上采用两阶段发酵法,并通过增加起始菌体浓度的方法,发酵生成的D-乳酸浓度达到83.5 g/L,光学纯度达到98.9%。本研究成果为使用粘质沙雷氏菌发酵生产D-乳酸的深入研究打下了基础。

The fermentative production of D-lactic acid by Serratia marcescens was investigated. Using Serratia marcescens Gl as the starting strain, the fermentation conditions of shake flask were determined： aerobic culture for the first 12 h as cell growth stage at 28℃, pH 7.0 ; anaerobic culture for the following 36 h as D-lactic acid accumulation phase at 44 ℃, pH 6.0. It was found that the glucose was preferred to the sucrose as carbon source for the synthesis of D-lactic acid. After screening, the strain R150 with tolerating high concentration of lactate was obtained from the start strain of genetically engineered strain R1 with lacking 2,3-butanediol synthesis pathway. The production of D-lactic acid combining two-stage fermentation and increasing the initial cell concentration was carried out in 3.7 L bioreactor by stain R150. The yield was as high as 83.5 g/L D-lactic acid with optical purity of 98.9%. This result laid the foundation of the further study for using Serratia marcescens to produce D-lactic acid.