摘要
基于质量守恒定律和代谢反应中间代谢物的拟稳态假设 ,定量研究了枯草芽孢杆菌 (Bacillussubtilis)代谢流分布随时间变化的特征。研究结果表明 ,在鸟苷发酵过程 40h左右 ,存在着从己糖单磷酸途径到酵解途径的代谢流迁移 ,所迁移的碳源主要生成了氨基酸和有机酸。定量研究的结果 ,为发酵过程的工艺优化提供了重要依据。
Metabolic engineering has become a powerful tool for optimization of industrial fermentation processes. Metabolic engineering usually undergoes three steps: construction of a recombinant strain with improved properties, genetic and biochemical analysis of the strain, and identification of target for further improvement. Metabolic fluxes analysis is an important part of the biochemical analysis. Based on the law of mass conservation and assuming pseudo-steady-state for the intermediates in the metabolic pathways, we have quantitatively analyzed the time course of the flux distribution in Bacillus subtilis and used the data to reveal the nature of the so-called “40 hour' phenomenon in fermentation of guanosine, a key raw material for the synthesis of additives for human consumption and animal feeds. The phenomenon refers to the observation that guanosine production, which proceeds at high rate from 12 hour on, declines around 40 hour while consumption of glucose keeps increasing, leading to the lower yield of the nucleoside. Equations based upon the metabolic network of Bacillus subtilis consisted of EMP pathway, HMP pathway, TCA cycle, oxidative phosphorylation pathway and others reactions of the intermediates, was constructed. The equations were solved by using the quantitative data obtained in this study. The air flow and volume, concentration of oxygen and carbon dioxide in the exit-gas were monitored online; the concentration of biomass, glucose and guanosine was analyzed manually; and the concentration of acetate, citric acid, pyruvate, and 17 amino acids were HPLC quantified. The solutions of the equation were proved to be valid, as the experimental data on oxygen consumption agrees with that of predicted form the equation. The results indicated that at 40h of the fermentation process the flux of HMP pathway, which provides the precursor of the nucleoside, decreased while that of EMP pathway and the pathways that generate amino acids and organic acids increased. The shift correlated with the accum
出处
《生物工程学报》
CAS
CSCD
北大核心
2003年第2期200-205,共6页
Chinese Journal of Biotechnology
基金
上海市曙光计划 (No :0 1SG2 8)
上海市重点学科项目资助。~~
