Synthesis of GDP-mannose using coupling fermentation of recombinant Escherichia coli.

Glucokinase (glk), phosphomannomutase (manB), and mannose-1-phosphate guanylytransferase (manC) are needed for the biosynthesis of GDP-mannose. A recombinant E. coli strain over-expressing these three genes was constructed to produce guanosine 5'-diphosphate (GDP)-mannose, the donor of GDP-fucose, an essential substrate for synthesis of fucosyloligosaccharides. In addition, the glk, manB, and manC genes were individually cloned into the expression vector pET-22b (+) to construct three recombinant E. coli strains pET-glk, pET-manB and pET-manC, respectively. Fermentation of the recombinant strain BL21/pET-glk-manB-manC had a conversion rate of 23% from mannose to GDP-mannose under IPTG induction, while coupling fermentation of the three recombinant strains BL21/pET-glk, BL21/pET-manB, BL21/pET-manC resulted in a conversion rate of 33% under the same induction conditions.