Reconstructing food colorants via synthetic biology: From microbial cell factories to sustainable biomanufacturing supply chains.

Food colorants constitute a critical segment of the global food industry, with an anticipated market valuation of USD 36.58 billion by 2030. Mounting safety apprehensions regarding synthetic dyes, illustrated by the recent ban on FD&C Red No. 3, have intensified the pursuit of sustainable natural substitutes. Concurrently, progress in synthetic biology and metabolic engineering has established microbial cell factories as a revolutionary system for the environmentally benign, large-scale production of these colorants. This review focuses on the microbial synthesis of food colorants in the three primary colors: red, yellow, and blue. We evaluate a comprehensive suite of multi-scale engineering methodologies, encompassing molecular-level enzyme refinement and pathway reconstitution, along with system-level transcriptional redesign, spatial engineering, and adaptive laboratory evolution. Furthermore, this review contrasts global regulatory frameworks and examines pivotal obstacles, including microbial safety, strain reproducibility, and technology translation from laboratory validation to industrial operation. In conclusion, we suggest prospective research initiatives designed to boost biosynthetic performance and robustness, with the goal of accelerating the industrial integration of bio-based colorants within a dynamically shifting regulatory and consumer context.