Fermentative production of the unnatural amino acid L-2-aminobutyric acid based on metabolic engineering

• Published in: Microbial cell factories Vol. 18; no. 1; p. 43
• Main Authors: Xu, Jian-Miao, Li, Jian-Qiang, Zhang, Bo, Liu, Zhi-Qiang, Zheng, Yu-Guo
• Format: Journal Article
• Language: English
• Published: England BioMed Central Ltd 28.02.2019; BioMed Central; BMC
• Subjects: Abscisic acid; Amino acids; Analysis; Bacteria; Batch culture; Bioreactors; Biosynthesis; Chemical synthesis; Chromosome deletion; Coliforms; CRISPR; Dehydrogenases; E coli; Environmental impact; Enzymes; Escherichia coli; Fed-batch fermentation; Fermentation; Gene deletion; Genes; Genetic engineering; Genomes; Glucose; Isoleucine; l-2-Aminobutyric acid; l-Leucine dehydrogenase; l-Threonine deaminase; Levetiracetam; Metabolic engineering; Metabolism; Metabolites; Novels; Physiological aspects; Threonine; L-2-Aminobutyric acid; Metabolic engineering; L-Leucine dehydrogenase; Fed-batch fermentation; L-Threonine deaminase
• ISSN: 1475-2859; 1475-2859
• DOI: 10.1186/s12934-019-1095-z

L-2-aminobutyric acid (L-ABA) is an unnatural amino acid that is a key intermediate for the synthesis of several important pharmaceuticals. To make the biosynthesis of L-ABA environmental friendly and more suitable for the industrial-scale production. We expand the nature metabolic network of Escherichia coli using metabolic engineering approach for the production of L-ABA. In this study, Escherichia coli THR strain with a modified pathway for threonine-hyperproduction was engineered via deletion of the rhtA gene from the chromosome. To redirect carbon flux from 2-ketobutyrate (2-KB) to L-ABA, the ilvIH gene was deleted to block the L-isoleucine pathway. Furthermore, the ilvA gene from Escherichia coli W3110 and the leuDH gene from Thermoactinomyces intermedius were amplified and co-overexpressed. The promoter was altered to regulate the expression strength of ilvA* and leuDH. The final engineered strain E. coli THR ΔrhtAΔilvIH/Gap-ilvA*-Pbs-leuDH was able to produce 9.33 g/L of L-ABA with a yield of 0.19 g/L/h by fed-batch fermentation in a 5 L bioreactor. This novel metabolically tailored strain offers a promising approach to fulfill industrial requirements for production of L-ABA.