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首页> 外文期刊>Applied Microbiology and Biotechnology >C-13-NMR analysis of glucose metabolism during citric acid production by Aspergillus niger
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C-13-NMR analysis of glucose metabolism during citric acid production by Aspergillus niger

机译：黑曲霉生产柠檬酸过程中葡萄糖代谢的C-13-NMR分析

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摘要

The effect of glucose concentration on glycolytic metabolism under conditions of citric acid accumulation by Aspergillus niger was studied with C-13-labelled glucose. The results show that during cultivation at high glucose (14%, w/v), most of the label in citric acid is in C-2/C-4, and is thus due to the pyruvate carboxylase reaction. However, a significant portion is also present in C-1/C-5, whose origin is less clear but most likely due to reconsumption of glycerol and erythritol. Formation of trehalose and mannitol is high during the early phase of fermentation and declines thereafter. The early fermentation phase is further characterized by a high rate of anaplerosis from oxaloacetate to pyruvate, which also decreases with time. At low glucose concentrations (2%, w/v), which lead to a significantly reduced citric acid yield and formation rate, labelling of citrate in C-2/C-4 is decreased and C-1/C-5 labelling increased. Growth on 2% glucose is also characterized by an appreciable scrambling of mannitol and considerable backflux from mannitol to trehalose (indicating tight glycolytic control at the fructose-6-phosphate step) and an increased anaplerotic formation of pyruvate from oxaloacetate. These data indicate that cultivation on high sugar concentrations shifts control of glycolysis from fructose-6-phosphate to the glyceraldehyde-3-phosphate dehydrogenase step. [References: 21]
机译：用C-13标记的葡萄糖研究了黑曲霉在柠檬酸积累条件下葡萄糖浓度对糖酵解代谢的影响。结果表明，在高葡萄糖（14％，w / v）下培养期间，柠檬酸中的大部分标记位于C-2 / C-4中，因此归因于丙酮酸羧化酶反应。但是，在C-1 / C-5中也存在很大一部分，其来源尚不清楚，但最有可能是由于甘油和赤藓糖醇的重新消耗。在发酵的早期，海藻糖和甘露醇的形成很高，此后下降。早期发酵阶段的特征还在于从草酰乙酸到丙酮酸的高比率的动脉粥样硬化，其也随着时间而减少。在低葡萄糖浓度（2％，w / v）下，这会导致柠檬酸收率和形成速率显着降低，C-2 / C-4中柠檬酸的标记减少，而C-1 / C-5标记增加。在2％的葡萄糖上生长的特征还在于甘露醇有明显的扰乱和大量的从甘露醇到海藻糖的回流（表明在6磷酸果糖步骤中严格的糖酵解控制），以及草酰乙酸中丙酮酸的无节律性形成增加。这些数据表明，在高糖浓度下的培养将糖酵解的控制从6-磷酸果糖转移到3-磷酸甘油醛脱氢酶步骤。 [参考：21]

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