文献类型：期刊文献

中文题名：鸟苷发酵过程的定量和优化:抑制NH_4^+离子积累提高了苷产量70%

英文题名：Quantitation & Optimization of Guanosine Fermentation Process: Prevention of NH_4^+ Accumulation Increases Guanosine Production by 70%

作者：黄明志[1];蔡显鹏[1];陈双喜[1];储炬[1];庄英萍[1];张嗣良[1]

机构：[1]华东理工大学生物反应器工程国家重点实验室生化工程技术研究中心生物工程学院,上海200237

年份：2003

卷号：19

期号：2

起止页码：200

中文期刊名：生物工程学报

外文期刊名：Chinese Journal of Biotechnology

收录：MEDLINE(收录号：15966322);CSTPCD;;Scopus;北大核心:【北大核心2000】；CSCD:【CSCD2011_2012】；PubMed;

基金：上海市曙光计划 (No :0 1SG2 8);上海市重点学科项目资助。~~

语种：中文

中文关键词：代谢流迁移;定量研究;鸟苷;枯草芽孢杆菌;代谢流分布

外文关键词：metabolic flux shift, quantitative analysis, Guanosine, Bacillus subtilis

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 accumulation of NH 4+ in the broth. The assimilation of NH 4+ is an energy consuming process and could shift the metabolism to the energy generating EMP pathway. Accordingly, measures were taken to prevent the accumulation of NH 4+. The interference indeed stopped the metabolism shift and boosted the guanosine production at 30 g/L, 70% higher than the level reported in literature.