1,3-丙二醇发酵过程中pH调控策略研究

Research on pH Control Strategy in the Bioconversion of Glycerol to 1,3-Propanediol

研究发现克雷伯氏肺炎杆菌利用甘油发酵产1,3-丙二醇过程中,发酵液的pH呈下降趋势,不仅影响了细胞的生长而且限制了1,3-丙二醇产量的提高。通过添加甘油和氨水的混合物维持恒定的pH提高了1,3-丙二醇的产量和转化率,但进一步研究发现不同pH条件下,副产物的组成明显不同,当pH为7.1—8.0时主要副产物是乳酸,而当pH为5.0—6.0时主要副产物是2,3-丁二醇。因此针对菌体细胞代谢对外界pH的不同应激效应,在补料过程中采取了pH波动的调控策略,通过控制底物甘油和氨水的比例和流加速率使发酵液的pH在6.3—7.3之间周期性地波动,最终2种主要副产物的量显著降低,1,3-丙二醇最大质量浓度高达70 g/L。

The fermentation process of 1, 3-propanediol （ 1, 3-PD） by Klebsiella pneumoniae with glycerol as substrate was researched both in batch and fed-batch system. The declining pH during this course led to a great many disadvantages to the growth of micrcorganism, and had a negative effect on the production of 1, 3-PD. In order to increase 1, 3-PD yield and to reduce byproduct formation, experiments were conducted in which different ratios of ammonia and glycerol mixtures were used for pH control as well as for supplementation of glycerol. During this course, an important phenomenon was noticed in that the yield of two main byproducts, 2, 3-butanediol and lactate, were closely related to pH. When pH was at 5,0 to 6, 0, the main byproduct was 2, 3-butanediol, however, when pH was at 7.1 to 8.0, the major byproduct changed to be lactate. Based on the different pH effect on the composition of the byproducts in the broth, a kind of pH control strategy was applied during which pH fluctuated between 6.3 and 7.3 periodically and at last the maximum concentration of 1, 3-PD reached 70 g/L.