Engineered Microbial Production of l -Fucose: A Sustainable Biomanufacturing Platform via Genomic Integration and Pathway Optimization

l-Fucose, a functional monosaccharide with high commercial potential in pharmaceuticals, nutraceuticals, and cosmetics, can be efficiently produced via microbial synthesis. This study established a robust l-fucose production platform through a comprehensive genomic integration and pathway optimization. Key GDP-l-fucose biosynthetic genes were chromosomally integrated with optimized constitutive synthetic promoters, enhancing the precursor supply and yielding 6.47 g/L l-fucose. Copy number amplification of the α1,2-fucosyltransferase gene (BKHT) further improved flux through the “GDP-l-fucose → 2′-FL → l-fucose” pathway. Crucially, growth-phase-dependent expression of α-l-fucosidase (afcA) using the stationary-phase promoter alleviated metabolic burden, boosting titer to 15.37 g/L. Combinatorial cofactor engineering prioritized biomass formation, while fed-batch fermentation with delayed lactose induction achieved 86.58 g/L l-fucose in 95 h─without plasmids, inducers, or antibiotics. This integrated strategy establishes a scalable industrial process for sustainable l-fucose biomanufacturing.