Dynamically metabolic engineering overflow metabolism for efficient production of l-alanine in Escherichia coli

l-Alanine, a key chiral amino acid with broad industrial applications, was previously synthesized via thermal-regulated fermentation using an engineered Escherichia coli B0016-060BC. Upon thermal induction optimization, this strain achieved 167.7 g/L l-alanine from glucose. A scarless genome editing system integrating sacB and tetA enabled deletion of the phosphotransacetylase gene (eutD), reducing acetate accumulation by 26.3 %. Dynamic control of glycolysis mediated by pyruvate-sensing minimized overflow metabolism with 87.9 % lower pyruvate, 67.4 % lower acetate, and substantially reduced byproducts derived from the tricarboxylic acid (TCA) cycle. Further attenuation of the TCA cycle via a degradation tag fused to pyruvate dehydrogenase decreased TCA-derived byproducts. The final strain B0016-090BC produced 195.2 g/L l-alanine with a yield of 88.6 g/100 g glucose and productivity of 3.07 g/L/h. This systematic metabolic engineering strategy significantly enhanced l-alanine production efficiency and purity, which was helpful to improve large-scale fermentation of l-alanine.