Production of itaconate by whole-cell bioconversion of citrate mediated by expression of multiple cis-aconitate decarboxylase (cadA) genes in Escherichia coli
Production of itaconate by whole-cell bioconversion of citrate mediated by expression of multiple cis-aconitate decarboxylase (cadA) genes in Escherichia coli
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DOI：
10.1007/s13278-017-0428-3
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发表时间：
2017-01-04
影响因子：
4.6
通讯作者：
Yang, Yung-Hun
中科院分区：
文献类型：
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作者：
Kim, Junyoung;Seo, Hyung-Min;Yang, Yung-Hun
将三合一闭合的概念应用于合著者网络意味着，如果学者们之前与同一个人合著，他们很可能发表一篇联合论文。先前的研究已经确定了中等至高（20%至40%）的关闭率；这一机制为未来合作者之间的联系提供了合理的解释。我们展示了如何基于闭包的先前操作实现计算三元闭包，即单模网络（NCC）的Newman度量和双模网络（OCC）的Opsahl度量，与通过我们在本文中引入和测试的度量随时间测量闭包相比，可能导致更高的闭包量。基于四个大型纵向数据集的实证实验，我们发现封闭率的下限为1-3%，上限为4-7%。这些结果激发了对合作关系形成的新解释因素的研究。衣康酸是一种C-5不饱和二羧酸，是一种重要的化学成分，用于制造高价值产品，如乳胶和高吸水性聚合物。衣康酸盐是由丝状真菌地曲霉发酵糖产生的。然而，土霉发酵过程发酵周期长，产生多种副产物，生产成本高。大肠杆菌已被开发为生产衣康酸的替代品。然而，葡萄糖发酵的转化率低，生产效率低。在这里，我们报道了通过控制多个cadA基因的表达，通过增强乌头酸酶和顺式乌头酸脱羧酶的活性，柠檬酸盐向衣康酸盐的全细胞生物转化。此外，该生物转化系统不需要使用缓冲液，从而降低了生产成本和净化过程中释放的副产物。使用该全细胞生物转化系统，我们能够在没有任何缓冲系统或额外辅助因子的情况下，从500 mM柠檬酸盐催化转化319.8 mM （41.6 g/L）的itaconate，在19 h内转化率为64.0%，生产率为2.19 g/L/h。我们的生物转化系统表明衣康酸的生产效率非常高。
Applying the concept of triadic closure to coauthorship networks means that scholars are likely to publish a joint paper if they have previously coauthored with the same people. Prior research has identified moderate to high (20 to 40%) closure rates; suggesting this mechanismis a reasonable explanation for tie formation between future coauthors. We show how calculating triadic closure based on prior operationalizations of closure, namely Newman's measure for one-mode networks (NCC) and Opsahl's measure for two-mode networks (OCC) may lead to higher amounts of closure compared to measuring closure over time via a metric that we introduce and test in this paper. Based on empirical experiments using four large-scale, longitudinal datasets, we find a lower bound of 1-3% closure rates and an upper bound of 4-7%. These results motivate research on new explanatory factors for the formation of coauthorship links.Itaconate, a C-5 unsaturated dicarboxylic acid, is an important chemical building block that is used in manufacturing high-value products, such as latex and superabsorbent polymers. Itaconate is produced by fermentation of sugars by the filamentous fungus Aspergillus terreus. However, fermentation by A. terreus involves a long fermentation period and the formation of various byproducts, resulting in high production costs. E. coli has been developed as an alternative for producing itaconate. However, fermentation of glucose gives low conversion yields and low productivity. Here, we report the whole-cell bioconversion of citrate to itaconate with enhanced aconitase and cis-aconitate decarboxylase activities by controlling the expression of multiple cadA genes. In addition, this bioconversion system does not require the use of buffers, which reduces the production cost and the byproducts released during purification. Using this whole-cell bioconversion system, we were able to catalyze the conversion of 319.8 mM of itaconate (41.6 g/L) from 500 mM citrate without any buffer system or additional cofactors, with 64.0% conversion in 19 h and a productivity of 2.19 g/L/h. Our bioconversion system suggests very high productivity for itaconate production.