Liao Yuling, Ye Yanrui, Wang Bin, Pan Li
School of Bioscience and Bioengineering, South China University of Technology, Guangzhou, 510006, Guangdong, China.
Star Lake Bioscience Co., Inc, Zhaoqing, 526060, Guangdong, China.
Biotechnol Lett. 2017 Nov;39(11):1675-1682. doi: 10.1007/s10529-017-2412-4. Epub 2017 Aug 24.
To deregulate the purine operon of the purine biosynthetic pathway and optimize energy generation of the respiratory chain to improve the yield of guanosine in Bacillus amyloliquefaciens XH7.
The 5'-untranslated region of the purine operon, which contains the guanine-sensing riboswitch, was disrupted. The native promoter Pw in B. amyloliquefaciens XH7 was replaced by different strong promoters. Among the promoter replacement mutants, XH7purE::P41 gave the highest guanosine yield (16.3 g/l), with an increase of 23% compared with B. amyloliquefaciens XH7. The relative expression levels of the purine operon genes (purE, purF, and purD) in the XH7purE::P41 mutant were upregulated. The concentration of inosine monophosphate (IMP), the primary intermediate in the purine pathway, was also significantly increased in the XH7purE::P41 mutant. Combined modification of the low-coupling branched respiratory chains (cytochrome bd oxidase) improved guanosine production synergistically. The final guanosine yield in the XH7purE::P41△cyd mutant increased by 41% to 19 g/l compared with B. amyloliquefaciens XH7.
The combined modification strategy used in this study is a novel approach to improve the production of guanosine in industrial bacterial strains.
解除嘌呤生物合成途径中嘌呤操纵子的调控，优化呼吸链的能量生成，以提高解淀粉芽孢杆菌XH7中鸟苷的产量。
破坏了包含鸟嘌呤感应核糖开关的嘌呤操纵子的5'非翻译区。用不同的强启动子替换了解淀粉芽孢杆菌XH7中的天然启动子Pw。在启动子替换突变体中，XH7purE::P41的鸟苷产量最高（16.3 g/l），与解淀粉芽孢杆菌XH7相比提高了23%。XH7purE::P41突变体中嘌呤操纵子基因（purE、purF和purD）的相对表达水平上调。嘌呤途径的主要中间产物肌苷单磷酸（IMP）的浓度在XH7purE::P41突变体中也显著增加。对低偶联分支呼吸链（细胞色素bd氧化酶）的联合修饰协同提高了鸟苷产量。与解淀粉芽孢杆菌XH7相比，XH7purE::P41△cyd突变体的最终鸟苷产量提高了41%，达到19 g/l。
本研究中使用的联合修饰策略是提高工业细菌菌株中鸟苷产量的一种新方法。
