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首页> 美国卫生研究院文献>International Journal of Biological Sciences >Influence of dissolved oxygen concentration on intracellular pH for regulation of Aspergillus niger growth rate during citric acid fermentation in a stirred tank bioreactor
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Influence of dissolved oxygen concentration on intracellular pH for regulation of Aspergillus niger growth rate during citric acid fermentation in a stirred tank bioreactor

机译：搅拌罐式生物反应器中柠檬酸发酵过程中溶解氧浓度对细胞内pH调节黑曲霉生长速率的影响

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摘要

In this paper we report the regulation of Aspergillus niger growth rate during citric acid fermentation in a stirred tank bioreactor. For this, the influence of dissolved oxygen concentration in a medium on intracellular pH values and consequently on overall microbial metabolism was emphasized. Intracellular pH of mycelium grown under different concentrations of dissolved oxygen in the medium was determined. Sensitivity of proteins toward proton concentration is well recognized, therefore pH influences on the activities of key regulatory enzymes of Aspergillus niger were determined at pH values similar to those detected in the cells grown under lower dissolved oxygen concentrations. The results have shown significantly reduced specific activities of hexokinase, 6-phosphofructokinase and glucose-6-phosphate dehydrogenase in more acidic environment, while pyruvate kinase was found to be relatively insensitive towards higher proton concentration. As expected, due to the reduced specific activities of regulatory enzymes under more acidic conditions, overall metabolism should be hindered in the medium with lower dissolved oxygen concentration which was confirmed by detecting the reduced specific growth rates. From the studies, we conclude that dissolved oxygen concentration affects the intracellular pH and thus growth rate of Aspergillus niger during the fermentation process.
机译：在本文中，我们报告了在搅拌罐式生物反应器中柠檬酸发酵过程中黑曲霉生长速率的调节。为此，强调了培养基中溶解氧浓度对细胞内pH值的影响，因此对整体微生物代谢的影响。测定在培养基中不同浓度的溶解氧下生长的菌丝体的细胞内pH。蛋白质对质子浓度的敏感性已得到公认，因此，在类似于在较低溶解氧浓度下生长的细胞中检测到的pH值下，确定了pH对黑曲霉关键调节酶活性的影响。结果表明，在更酸性的环境中，己糖激酶，6-磷酸果糖激酶和葡萄糖-6-磷酸脱氢酶的比活性显着降低，而丙酮酸激酶对更高的质子浓度相对不敏感。如所预期的，由于在更酸性条件下调节酶的比活性降低，因此应在溶解氧浓度较低的培养基中阻碍总体代谢，这可通过检测降低的比生长速率来证实。从研究中，我们得出结论，在发酵过程中，溶解氧浓度会影响细胞内pH值，从而影响黑曲霉的生长速率。

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