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.

中文翻译：

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工程大肠杆菌中的 Menaquinone-7 生产

Menaquinone-7 (MK-7) 是维生素 K2 系列中极有价值的成员，是人体必需的营养素。在这项研究中，为了开发用于生产 MK-7 的工程大肠杆菌菌株，引入了异质七异戊二烯焦磷酸合成酶 (HepPPS)，并通过枯草芽孢杆菌衍生的 HepPPS (BsHepPPS) 的过表达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，使MK-7的滴度增加到2.3 μM，是原菌株的22倍。通过删除 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和 13.6 μM (8. 8 mg/L) 获得了 MK-7。此外，代谢物分析揭示了 ubiE MK-7 通路的新瓶颈，为进一步优化提供了一条途径。本报告首次描述了 MK-7 在大肠杆菌中的代谢工程，为 MK-7 的生产提供了新的视角。