Metabolic Engineering of Escherichia coli for Self-Induced Production of l-Isoleucine

As one of the three important branched-chain amino acids, l-isoleucine has a wide range of applications in the fields of medicine, food, and feed. Currently, the production of l-isoleucine is well-studied by Corynebacterium glutamicum, while the autonomous and efficient production of l-isoleucine in Escherichia coli has not been reported. Here, we developed a production strategy that combined metabolic engineering with bacterial quorum sensing to achieve the efficient production of l-isoleucine. First, we enhanced the l-isoleucine synthesis pathway by overexpressing the genes ilvIH1, CgilvA1, and ygaZH. Second, the precursor supply was increased by knocking out the gene rhtC, while deletion of the gene livJ was implemented to maximize the accumulation of l-isoleucine. Finally, the artificial quorum sensing system was applied to the efficient production of l-isoleucine, and self-induced protein expression in E. coli was realized through self-regulation during fermentation. In this study, an l-threonine high-yielding strain of E. coli TWF106 was used as the starting strain, and the final strain TWF127/pST1011, pST1042-IH1ZHA1 obtained 49.3 g/L l-isoleucine with a yield of 0.32 g/g glucose and a productivity of 1.03 g/(L·h). This autonomous production strategy without the addition of inducers can also be used in other biosynthetic pathways to increase yields while also providing the possibility for various natural products to be applied to industrial production.