Menaquinone-7 production in engineered Escherichia coli.

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.