Microbial Manufacturing and Application of trans-Aconitic Acid.

trans-Aconitic acid, an unsaturated tricarboxylic acid, possesses considerable application potential in agriculture, biomaterials, and green chemistry, owing to its distinct chemical structure and thermodynamic stability. However, its industrial-scale production has long been hampered by the limited yields of plant extraction methods, as well as the economic and environmental drawbacks associated with chemical synthesis. This review systematically outlines the advances in the production and application of trans-Aconitic acid, with a specific focus on breakthroughs in microbial manufacturing. Through systematic metabolic engineering of industrial Aspergillus terreus, a high-titer trans-Aconitic acid cell factory was successfully developed. Subsequent optimization of the fermentation medium and process parameters enabled the establishment of a robust and scalable fermentation process, which was successfully validated in a 120 m3 fermenter. In parallel, a green and efficient downstream process was designed to overcome challenges related to high solubility and complex impurity profiles of the fermentation broth, leading to the creation of the first industrial trans-Aconitic acid production line. These technological breakthroughs have facilitated commercial application of trans-Aconitic acid in two key areas: bionematicide formulations for sustainable crop protection and bio-based plasticizers of trans-Aconitates. The progress summarized in this review positions trans-Aconitic acid as a promising bio-based platform chemical and outlines a replicable route from laboratory innovation to industrial implementation for bio-derived organic acids.