Collaborative Innovation Center of Modern Biological Breeding of Henan Province, Xinxiang, 453003, China.
School of Life Science and Technology, Henan Institute of Science and Technology, 90 Hualan Road, Xinxiang, 453003, Henan Province, China.
Biotechnol Lett. 2021 Oct;43(10):1989-1999. doi: 10.1007/s10529-021-03170-6. Epub 2021 Aug 14.
In our previous study, citrate was used as auxiliary energy substance for improving cAMP fermentation performance, however, the regulation mechanism of citrate on improved cAMP contents was not clear. To elucidate the regulation mechanism, cAMP fermentations with/without citrate addition were conducted in a 7 L fermentor using Arthrobacter sp. CCTCC 2013431 and assays on key enzymes activities, energy metabolism level, amino acids contents and peroxidation level were performed.
With 3 g/L-broth sodium citrate added, cAMP concentration and conversion yield from glucose reached 4.34 g/L and 0.076 g/g which were improved by 30.7% and 29.8%, respectively, when compared with those of control. Citrate changed carbon flux distribution among different routes and more carbon flux was directed into pentose phosphate pathway beneficial to cAMP synthesis. Meanwhile, energy metabolism together with precursor amino acids levels were improved significantly owing to strengthened metabolic intensity of tricarboxylate cycle by exogenous citrate utilization which provided energy and substance basis for cAMP production. Moreover, higher glutamate synthesis and oxidative stress caused by citrate addition consumed excessive NADPH derived from pentose phosphate pathway by which feedback suppression for pentose phosphate pathway was relieved efficiently.
Citrate promoted cAMP fermentation production by Arthrobacter sp. CCTCC 2013431 due to enhanced precursor amino acids, energy metabolism level and relieved feedback suppression for pentose phosphate pathway.
在我们之前的研究中，使用柠檬酸盐作为辅助能量物质来提高 cAMP 发酵性能，然而，柠檬酸盐对提高 cAMP 含量的调节机制尚不清楚。为了阐明调节机制，在 7 L 发酵罐中使用节杆菌 CCTCC 2013431 进行了有/无柠檬酸盐添加的 cAMP 发酵，并对关键酶活性、能量代谢水平、氨基酸含量和过氧化水平进行了测定。
添加 3 g/L-培养基柠檬酸钠后，cAMP 浓度和葡萄糖转化率分别达到 4.34 g/L 和 0.076 g/g，分别提高了 30.7%和 29.8%。与对照组相比。柠檬酸盐改变了不同途径的碳通量分布，更多的碳通量被引导到戊糖磷酸途径，有利于 cAMP 的合成。同时，由于外源性柠檬酸的利用增强了三羧酸循环的代谢强度，能量代谢和前体氨基酸水平也得到了显著改善，为 cAMP 生产提供了能量和物质基础。此外，由于柠檬酸的添加增加了谷氨酸的合成和氧化应激，导致来自戊糖磷酸途径的 NADPH 消耗过多，从而有效地缓解了戊糖磷酸途径的反馈抑制。
柠檬酸通过增强前体氨基酸、能量代谢水平和缓解戊糖磷酸途径的反馈抑制作用，促进了节杆菌 CCTCC 2013431 的 cAMP 发酵生产。
