Menaquinone-7 production in engineered Escherichia coli
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(2020) 36:132
ORIGINAL PAPER
Menaquinone‑7 production in engineered Escherichia coli Quanxiu Gao1,2 · Hao Chen2,3 · Wenzhao Wang4 · Jianzhong Huang1 · Yong Tao2,3 · Baixue Lin2,3 Received: 17 March 2020 / Accepted: 27 June 2020 © Springer Nature B.V. 2020
Abstract 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. Graphic abstract
Keywords Engineered escherichia coli · Heptaprenyl pyrophosphate synthetase · Menaquinone-7 · Mevalonic acid pathway
Electronic supplementary material The online version of this article (https://doi.org/10.1007/s11274-020-02880-9) contains supplementary material, which is available to authorized users. * Jianzhong Huang [email protected] * Baixue Lin [email protected] Extended author information available on the last page of the article
Introduction MK-7 has a wide range of biological functions in the human body, such as treating Parkinson’s disease and osteoporosis (Berenjian et al. 2015). Therefore, MK-7 has strong application prospects and possesses high market value in food, health, and medicine. Since the content of MK-7 in natural food is extremely low, MK-7 is mainly produced by fermentation of
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Bacillus species (Berenjian et al. 2015; Beulens et al. 2009; Mahdinia et al. 2017, 2019). B. subtilis is considered the dominant and most promising potential strain for microbial production of MK-7 due to its long history of research and high content of MK-7. However, the process of fermentation by B. subtilis usually takes a long time (approximately six days). Although metabolic engineering of B. subtilis for MK-7 continues to progress, the productivity of MK-7 is low, and the fermentation cost of B. subtilis remains high, which keeps the global price of MK-7 high (Ma et al. 2019; Yang et al. 2019). Escherichia coli, which is fast-growing and easy to manipulate, has been studied extensively on a fundamental and applied level and has become a predominant host microorganis
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