Microbial Synthesis of l-Fucose with High Productivity by a Metabolically Engineered Escherichia coli

l-Fucose is a natural deoxy hexose found in a variety of organisms. It possesses many physiological effects and has potential applications in pharmaceutical, cosmetic, and food industries. Microbial synthesis via metabolic engineering attracts increasing attention for efficient production of important chemicals. Previously, we reported the construction of a metabolically engineered Escherichia coli strain with high 2'-fucosyllactose productivity. Herein, we further introduced Bifidobacterium bifidum α-l-fucosidase via both plasmid expression and genomic integration and blocked the l-fucose assimilation pathway by deleting fucI, fucK, and rhaA. The highest l-fucose titers reached 6.31 and 51.05 g/L in shake-flask and fed-batch cultivation, respectively. l-Fucose synthesis was little affected by lactose added, and there was almost no 2'-fucosyllactose residue throughout the cultivation processes. The l-fucose productivity reached 0.76 g/L/h, indicating significant potential for large-scale industrial applications.