Lin Y H, Bayrock D, Ingledew W M
Department of Chemical Engineering and Department of Applied Microbiology and Food Sciences, University of Saskatchewan, Saskatoon, Saskatchewan, Canada S7N 5C9.
Biotechnol Prog. 2001 Nov-Dec;17(6):1055-60. doi: 10.1021/bp0101029.
The technique of metabolic flux analysis was implemented to elucidate the flux balancing of Saccharomyces cerevisiae cultivated in a multistage continuous stirred tank reactor fermentation environment. The results showed that the majority of the substrate (97.70 +/- 0.49%) was funneled into the glycolytic pathway, while the remainder was subdivided between the pentose phosphate pathway and pathways for polysaccharide synthesis. At the pyruvate node, 87.30 +/- 1.38% of the flux was channeled through the reaction governed by pyruvate decarboxylase. Fluxes through the pyruvate dehydrogenase bypass were maintained at a constant level (82.65 +/- 1.47%) irrespective of the configuration of the fermentation setup. Activity through the TCA "cycle" was replenished by the reaction catalyzed by pyruvate carboxylase and by the transport of cytosolic oxaloacetate across the mitochondrial membrane. The CO(2) evolution rate varied as fermentation progressed; however, the yield coefficient of CO(2) remained at a constant value. Although a constant yield of ethanol (0.42 g of ethanol/g of glucose) was obtained, operations of the TCA cycle were gradually switched from partially reductive to partially oxidative pathways from the first fermenter to the fourth fermenter.
运用代谢通量分析技术来阐明在多级连续搅拌釜式反应器发酵环境中培养的酿酒酵母的通量平衡。结果表明，大部分底物（97.70±0.49%）进入糖酵解途径，其余部分则在磷酸戊糖途径和多糖合成途径之间分配。在丙酮酸节点，87.30±1.38%的通量通过丙酮酸脱羧酶催化的反应进行传递。无论发酵装置的配置如何，通过丙酮酸脱氢酶旁路的通量都维持在恒定水平（82.65±1.47%）。通过三羧酸（TCA）“循环”的活性通过丙酮酸羧化酶催化的反应以及胞质草酰乙酸穿过线粒体膜的转运得以补充。随着发酵的进行，二氧化碳释放速率发生变化；然而，二氧化碳的产率系数保持恒定。尽管获得了恒定的乙醇产率（0.42克乙醇/克葡萄糖），但从第一个发酵罐到第四个发酵罐，三羧酸循环的运行逐渐从部分还原途径转变为部分氧化途径。
