Metabolic engineering of Escherichia coli for the efficient production of l-threonine

• Published in: Systems Microbiology and Biomanufacturing 2024-04, Vol.4 (2), p.810-819
• Main Authors: Yang, Hao, Hou, Ying-Jie, Xu, Jian-Zhong, Zhang, Wei-Guo
• Format: Article
• Language: English
• Subjects: Biomedical and Life Sciences; Biomedical Engineering and Bioengineering; Food Microbiology; Life Sciences; Metabolomics; Microbiology; Original Article
• ISSN: 2662-7655; 2662-7663
• DOI: 10.1007/s43393-023-00183-2

l -Threonine is an important amino acid, which can be added in food, medicine or feed. In this paper, an l -threonine-producing strain was constructed using a modified CRISPR gene editing technology. Here, it was verified that the mutation of glycine at position 433 of aspartate kinase AKI to arginine ( thrA G1297A ) relieve effectively the feedback inhibition of AKI by l -threonine. The trc promoter replaced the native promoter of thrA in the Escherichia coli XQ-12 genome, and thus increasing its expression level. Moreover, by modifying the glycolytic pathway, disruption of phosphofructokinase encoded by the gene pfkA and pyruvate kinase encoded by the gene pykF increased l -threonine production. Then, the ppc gene encoding phosphoenolpyruvate carboxylase was overexpressed by replacing its native promoter with the core- trc promoter, which slightly improved the growth of the l -threonine-producing strain E. coli XQ-12 as well as the l -threonine production. In addition, it was found that further absence of the gene crr in the PTS system and the gene tdh encoding threonine dehydrogenase improved significantly l -threonine production. The final amounts of l -threonine produced by plasmid-free, antibiotic-free and inducer-free strains E. coli XQ-12.4 were 127.3 g/L and 3.536 g/L/h, respectively, in fed-batch fermentation.