Lee Ming-Yi, Hung Wen-Pin, Tsai Shu-Hsien
Department of Nutrition and Health Sciences, Research Center for Food and Cosmetic Safety, and Research Center for Chinese Herbal Medicine, College of Human Ecology, Chang Gung University of Science and Technology, Kweishan, Taoyuan, Taiwan.
Material and Chemical Research Laboratories, Industrial Technology Research Institute, Hsinchu, Taiwan.
World J Microbiol Biotechnol. 2017 Feb;33(2):25. doi: 10.1007/s11274-016-2192-3. Epub 2017 Jan 2.
Shikimic acid is an important metabolic intermediate with various applications. This paper presents a novel control strategy for the construction of shikimic acid producing strains, without completely blocking the aromatic amino acid biosynthesis pathways. Growth phase-dependent expression and gene deletion was performed to regulate the aroK gene expression in the shikimic acid producing Escherichia coli strain, SK4/rpsM. In this strain, the aroL and aroK genes were deleted, and the aroB, aroG*, ppsA, and tktA genes were overexpressed. The relative amount of shikimic acid that accumulated in SK4/rpsM was 1.28-fold higher than that in SK4/pLac. Furthermore, a novel shikimic acid production pathway, combining the expression of the dehydroquinate dehydratase-shikimate dehydrogenase (DHQ-SDH) enzyme from woody plants, was constructed in E. coli strains. The results demonstrated that a growth phase-dependent control of the aroK gene leads to higher SA accumulation (5.33 g/L) in SK5/pSK6. This novel design can achieve higher shikimic acid production by using the same amount of medium used by the current methods and can also be widely used for modifying other metabolic pathways.
莽草酸是一种具有多种用途的重要代谢中间体。本文提出了一种构建产莽草酸菌株的新型控制策略，该策略不会完全阻断芳香族氨基酸生物合成途径。通过进行生长阶段依赖性表达和基因缺失来调节产莽草酸的大肠杆菌菌株SK4/rpsM中的aroK基因表达。在该菌株中，aroL和aroK基因被缺失，而aroB、aroG*、ppsA和tktA基因被过表达。SK4/rpsM中积累的莽草酸相对量比SK4/pLac中的高1.28倍。此外，在大肠杆菌菌株中构建了一条新的莽草酸生产途径，该途径结合了木本植物中脱氢奎尼酸脱水酶-莽草酸脱氢酶（DHQ-SDH）的表达。结果表明，aroK基因的生长阶段依赖性控制导致SK5/pSK6中莽草酸积累量更高（5.33 g/L）。这种新设计使用与当前方法相同量的培养基就能实现更高的莽草酸产量，并且还可广泛用于修饰其他代谢途径。
