National Engineering Research Center of Industrial Microbiology and Fermentation Technology, College of Life Sciences, Fujian Normal University, Fuzhou, 350117, Fujian, China.
CAS Key Laboratory of Microbial Physiological and Metabolic Engineering, State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing, 100101, China.
World J Microbiol Biotechnol. 2020 Aug 1;36(9):132. doi: 10.1007/s11274-020-02880-9.
Menaquinone-7 (MK-7), a highly valuable member of the vitamin K2 series, is an essential nutrient for humans. In this study, to develop engineered Escherichia coli strains for MK-7 production, heterogeneous heptaprenyl pyrophosphate synthetase (HepPPS) was introduced, and MK-7 production was first achieved in engineered E. coli by overexpression of Bacillus subtilis-derived HepPPS (BsHepPPS). Then, by optimizing the enzyme expression of the heterogenous mevalonic acid (MVA) pathway and the BsHepPPS, the titre of MK-7 increased to 2.3 μM, which was 22-fold higher than that of the original strain. The competitive pathways of MK-7 were further investigated by deletion of ubiCA or ispB. Finally, the scale-up fermentation of the engineered E. coli in a 5-L fermenter was studied under aerobic conditions using glucose, and 13.6 μM (8.8 mg/L) MK-7 was achieved. Additionally, metabolite analysis revealed a new bottleneck in the MK-7 pathway at ubiE, suggesting an avenue for further optimization. This report is the first to describe the metabolic engineering of MK-7 in E. coli, which provides a new perspective for MK-7 production.
甲萘醌-7（MK-7）是维生素 K2 系列中极具价值的成员，是人体必需的营养物质。在这项研究中，为了开发用于 MK-7 生产的工程大肠杆菌菌株，引入了异戊烯基焦磷酸合酶（HepPPS），并通过过表达枯草芽孢杆菌衍生的 HepPPS（BsHepPPS）首次在工程大肠杆菌中实现了 MK-7 的生产。然后，通过优化异源甲羟戊酸（MVA）途径和 BsHepPPS 的酶表达，MK-7 的产量增加到 2.3 μM，比原始菌株高 22 倍。通过缺失 ubiCA 或 ispB 进一步研究了 MK-7 的竞争途径。最后，在有氧条件下使用葡萄糖在 5-L 发酵罐中研究了工程大肠杆菌的放大发酵，获得了 13.6 μM（8.8 mg/L）的 MK-7。此外，代谢物分析在 ubiE 处揭示了 MK-7 途径中的一个新瓶颈，表明有进一步优化的途径。本报告首次描述了大肠杆菌中 MK-7 的代谢工程，为 MK-7 的生产提供了新的视角。
