Breaking the bottleneck of the α-ketopimelate pathway to boost adipic acid synthesis in Escherichia coli via metabolic and enzymatic engineering

Adipic acid, as one of the dicarboxylic acids, has a wide application in the production of biodegradable plastic materials. The α-ketopimelate (AKP) pathway offers a viable route for the biosynthesis of adipic acid, which was explored in the engineered Escherichia coli. Coupled with the optimization of heterologous enzyme expression, the regulation of byproduct acetic acid accumulation, and the modification of rate-limiting enzyme catalyzed by high-citrate synthase, 0.79 g/L adipic acid was achieved in shake flasks. Furthermore, enzyme kinetics and molecular simulations analysis were conducted to clarify the molecular mechanism responsible for the increased catalytic activity of the high-citrate synthase mutant Nivf (G345S). And fed-batch fermentation was conducted in a 5 L bioreactor, which boosted the adipic acid titer to 3.89 g/L. Our work demonstrates the potential of the AKP pathway for adipic acid synthesis while providing a platform for the synthesis of other high-value dicarboxylic acids.