From transport to regulation: systems engineering for high-efficiency dicarboxylic acid biosynthesis

Medium- and long-chain dicarboxylic acids (M/LCDAs) are key monomers for the synthesis of nylons and high-performance engineering plastics. Compared to traditional chemical methods, microbial synthesis offers advantages such as environmental friendliness and high regioselectivity. However, its industrial application remains limited by bottlenecks, including low mass transfer efficiency on hydrophobic substrates, instability of key oxidase systems, and cellular metabolic imbalances. This review summarizes recent strategies leveraging enzyme engineering, systems metabolic engineering, and diverse synthetic biology approaches to overcome current limitations in the biosynthesis of M/LCDAs. We specifically highlight mechanisms for enhancing the transmembrane transport of hydrophobic substrates and the mining of novel transporters. Furthermore, we elaborate on protein engineering efforts targeting key enzymes (e.g. cytochrome P450s), covering rational design, fusion expression, and novel dimerization techniques. At the systems level, we discuss metabolic network regulation achieved through the construction of the reverse β-oxidation cycle (r-BOX) and the reprogramming of cofactor regeneration and energy metabolism. Finally, future perspectives on integrating AI-aided design and waste valorization are proposed to provide theoretical guidance for the efficient and sustainable biomanufacturing of M/LCDAs.