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首页> 外文期刊>Applied Microbiology >Key Process Conditions for Production of C4 Dicarboxylic Acids in Bioreactor Batch Cultures of an Engineered Saccharomyces cerevisiae Strain
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Key Process Conditions for Production of C4 Dicarboxylic Acids in Bioreactor Batch Cultures of an Engineered Saccharomyces cerevisiae Strain

机译：酿酒酵母菌株生物反应器批培养中生产C4二羧酸的关键工艺条件

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A recent effort to improve malic acid production by Saccharomyces cerevisiae by means of metabolic engineering resulted in a strain that produced up to 59 g liter~(?1) of malate at a yield of 0.42 mol (mol glucose)~(?1) in calcium carbonate-buffered shake flask cultures. With shake flasks, process parameters that are important for scaling up this process cannot be controlled independently. In this study, growth and product formation by the engineered strain were studied in bioreactors in order to separately analyze the effects of pH, calcium, and carbon dioxide and oxygen availability. A near-neutral pH, which in shake flasks was achieved by adding CaCO_(3), was required for efficient C_(4) dicarboxylic acid production. Increased calcium concentrations, a side effect of CaCO_(3) dissolution, had a small positive effect on malate formation. Carbon dioxide enrichment of the sparging gas (up to 15% [vol/vol]) improved production of both malate and succinate. At higher concentrations, succinate titers further increased, reaching 0.29 mol (mol glucose)~(?1), whereas malate formation strongly decreased. Although fully aerobic conditions could be achieved, it was found that moderate oxygen limitation benefitted malate production. In conclusion, malic acid production with the engineered S. cerevisiae strain could be successfully transferred from shake flasks to 1-liter batch bioreactors by simultaneous optimization of four process parameters (pH and concentrations of CO_(2), calcium, and O_(2)). Under optimized conditions, a malate yield of 0.48 ± 0.01 mol (mol glucose)~(?1) was obtained in bioreactors, a 19% increase over yields in shake flask experiments.
机译：最近通过代谢工程改进酿酒酵母生产苹果酸的努力导致菌株产生了高达59 g升〜（？1）的苹果酸，其产量为0.42 mol（mol葡萄糖）〜（？1）。碳酸钙缓冲的摇瓶培养。对于摇瓶，不能独立控制对于扩大此过程很重要的过程参数。在这项研究中，在生物反应器中研究了工程菌株的生长和产物形成，以便分别分析pH，钙，二氧化碳和氧气的利用率。有效的C_（4）二羧酸生产需要在摇瓶中通过添加CaCO_（3）达到接近中性的pH值。钙浓度升高是CaCO_（3）溶解的副作用，对苹果酸的形成有较小的积极影响。喷射气体的二氧化碳富集（高达15％（体积/体积））提高了苹果酸和琥珀酸的产量。在较高浓度下，琥珀酸滴度进一步增加，达到0.29 mol（mol葡萄糖）〜（？1），而苹果酸的形成强烈下降。尽管可以达到完全有氧的条件，但是发现适度的氧气限制有益于苹果酸的生产。总之，通过同时优化四个工艺参数（pH值和CO_（2），钙和O_（2）的浓度），可以将工程酿酒酵母菌株生产的苹果酸成功地从摇瓶转移到1升分批生物反应器中。 ）。在最佳条件下，在生物反应器中苹果酸收率为0.48±0.01 mol（mol葡萄糖）〜（？1），比摇瓶实验的收率高19％。

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