School of Chemical Engineering and Technology, Tianjin University, Tianjin, 300072, China.
State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing, 100190, China.
Appl Biochem Biotechnol. 2021 Oct;193(10):3045-3061. doi: 10.1007/s12010-021-03584-y. Epub 2021 May 15.
The metabolic processes involved in simultaneous production of vitamin B and propionic acid by Propionibacterium freudenreichii are very complicated. To further investigate the regulatory mechanism of this metabolism, a simplified metabolic network was established. The effects of glucose feeding, propionic acid removal, and 5,6-dimethylbenzimidazole (DMB) addition on the metabolic flux distribution were investigated. The results showed that synthesis of propionic acid can be increased by increasing the metabolic flux through the oxaloacetate and methylmalonyl-CoA branches in the early and middle stages of the coupled fermentation. After DMB addition, the synthesis of vitamin B was significantly enhanced via increased metabolic flux through the δ-aminolevulinate branch, which promoted the synthesis of uroporphyrinogen III, a precursor of vitamin B. Therefore, the analysis of metabolic flux at key nodes can provide theoretical guidance for the optimization of P. freudenreichii fermentation processes. In an experimental coupled fermentation process, the concentrations of vitamin B and propionic acid reached 21.6 and 50.12 g/L respectively, increased by 105.71% and 73.91% compared with batch fermentation, which provides a new strategy for industrial production.
丙酸杆菌同时生产维生素 B 和丙酸的代谢过程非常复杂。为了进一步研究该代谢的调控机制，建立了简化的代谢网络。考察了葡萄糖流加、丙酸去除和 5,6-二甲基苯并咪唑（DMB）添加对代谢通量分布的影响。结果表明，在耦合发酵的早期和中期，通过增加草酰乙酸和甲基丙二酰辅酶 A 分支的代谢通量，可以增加丙酸的合成。DMB 添加后，通过增加 δ-氨基乙酰丙酸分支的代谢通量，显著增强了维生素 B 的合成，从而促进了维生素 B 的前体尿卟啉原 III 的合成。因此，关键节点的代谢通量分析可为优化丙酸杆菌发酵过程提供理论指导。在实验耦合发酵过程中，维生素 B 和丙酸的浓度分别达到 21.6 和 50.12 g/L，与分批发酵相比分别提高了 105.71%和 73.91%，为工业生产提供了新策略。
