De novo biosynthesis of α-aminoadipate via multi-strategy metabolic engineering in Escherichia coli

As a non-protein amino acid, alpha-aminoadipate is used in the fields of medicine, chemical engineering, food science, and others. For example, alpha-aminoadipate is an important precursor for the production of beta-lactam antibiotics. Currently, the synthesis of alpha-aminoadipate depends on chemical catalysis that has the disadvantages of high cost, low yield, and serious pollution. In this study, we construct a biosynthesis pathway of alpha-aminoadipate in Escherichia coli using lysine as a precursor. In addition, we regulate the cell metabolism to improve the titer of alpha-aminoadipate via multi-strategy metabolic engineering. First, a novel synthetic pathway was constructed to realize de novo synthesis of alpha-aminoadipate with titers of 82 mg/L. Second, the key enzymes involved in enhancing precursor synthesis were overexpressed and the CO2 fixation process was introduced, and these led to 80% and 34% increases in the alpha-aminoadipate concentration, reaching 147 and 110 mg/L, respectively. Third, cofactor regulation was used to maintain the coupling balance of material and energy, with the intracellular alpha-aminoadipate concentration reaching 140 mg/L. Fourth, the weakening of the synthesis of acetic acid was used to strengthen the synthesis of alpha-aminoadipate, and this resulted in the enhancement of the alpha-aminoadipate concentration by 2.2 times, reaching 263 mg/L. Finally, combination optimization was used to promote the production of alpha-aminoadipate. The titers of alpha-aminoadipate reached 368 mg/L (strain EcN11#) and 415 mg/L (strain EcN11##), which was 3.5 and 4 times higher than that of the parent strain. With these efforts, 1.54 g/L of alpha-aminoadipate was produced under fed-batch conditions by strain EcN11#. This study is the first to present the effective biosynthesis of alpha-aminoadipate in E. coil using mufti-strategy metabolic engineering.