High efficiency production of 5-hydroxyectoine using metabolically engineered Escherichia coli

• Published in: Bioresource technology 2024-12, Vol.413, p.131493, Article 131493
• Main Authors: Qin, Zhijie, Li, Lihong, Zeng, Weizhu, Li, Hongbiao, Zhou, Jingwen, Xu, Sha
• Format: Article
• Language: English
• Subjects: Ectoine hydroxylase; Glyoxylate cycle; Low-salt synthesis process; Semi-continuous feeding process
• ISSN: 0960-8524; 1873-2976; 1873-2976
• DOI: 10.1016/j.biortech.2024.131493

[Display omitted] •Activated the glyoxylate cycle to enhance 5-hydroxyectoine synthesis.•Introduced a dynamic regulatory element to redistribute α-ketoglutarate flux.•Synthesized 58 g/L 5-hydroxyectoine with a glucose conversion rate of 260 mg/g.•Established a low salt synthesis process for 5-hydroxyectoine production. The 5-hydroxyectoine is a natural protective agent with long-lasting moisturising and radiation resistance properties. It can be naturally synthesized by some extremophiles using the “bacterial milking” process, but this can corrode bioreactors and downstream purification may cause environmental pollution. In this study, an engineered Escherichia coli (E. coli) strain was constructed for the 5-hydroxyectoine production. First, three ectoine hydroxylases were characterised and the enzyme from Halomonas elongata was the most effective. The L-2,4-diaminobutyrate transaminase mutant was introduced into the engineered strain, which could accumulate 2.8 g/L 5-hydroxyectoine in shake flasks. By activating the glyoxylate cycle and balancing the α-ketoglutarate distribution, the 5-hydroxyectoine titer was further increased to 3.4 g/L. Finally, the optimized strain synthesized 58 g/L 5-hydroxyectoine via a semi-continuous feeding process in a NaCl-free medium. Overall, this study reported the highest titer of 5-hydroxyectoine synthesized by E. coli and established a low-salt fermentation process through the aforementioned efforts.