甜菜碱作为一种新型的发酵助剂,能够有效提升工业生产过程中菌株的发酵性能。以苏氨酸生产菌Escherichia coli THRD 为研究对象,系统考察了甜菜碱对苏氨酸发酵以及菌体胞内代谢的影响。发酵过程中添加甜菜碱,苏氨酸产量从50.74 g/L提高到54.59 g/L,糖酸转化率从37.45%提高到40.69%。使用超高效液相色谱-飞行时间质谱联用技术分析甜菜碱作用下菌体胞内代谢物含量的变化,发现28个与苏氨酸合成代谢相关的显著差异代谢物。代谢通路分析表明,甜菜碱的加入能够通过改变糖酵解和磷酸戊糖途径的碳流分配,动态调节磷酸烯醇式丙酮酸羧化酶催化的CO2固定反应和三羧酸循环,减少3-磷酸甘油醛、天冬氨酸和苏氨酸的支路代谢,为苏氨酸的合成提供充足的还原力和前体物。研究从代谢层面揭示了甜菜碱对大肠杆菌的作用效果,为甜菜碱在其他工业发酵产品中的应用提供了理论参考。
Betaine can effectively improve the fermentation performance of strains in industrial production. The effect of betaine on threonine fermentation and intracellular metabolism of Escherichia coli THRD were investigated. The threonine titer increased from 50.74 g/L to 54.59 g/L, while the yield increased from 37.45% to 40.69% when betaine was fed. In such case, 28 significantly different metabolites related threonine anabolism were discovered. Metabolic flux analysis showed that carbon flow distribution of glycolysis and pentose phosphate pathway were changed, CO2 fixation reaction catalyzed by phosphoenol pyruvate carboxylase and tricarboxylic acid cycle were regulated, and bypass metabolism of glyceraldehyde-3-phosphate, aspartic acid and threonine were reduced, thus providing sufficient reducing power and precursor for threonine synthesis. The results revealed the effect of betaine on E. coli on the metabolic level and provided a theoretical reference for the application of betaine in other industrial fermentation products.
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