Colanic Acid: Biosynthetic Overproduction by Engineering Escherichia coli and Physical Property Characterization

Colanic acid has promising applications in food, cosmetic, and healthcare fields. In this study, a recombinant WQM003/pRAU was constructed by deleting genes lon and hns and overexpressing genes rcsA and galU in E. coli MG1655Δ(L-Q). After systematic optimization of fermentation conditions, colanic acid yield in WQM003/pRAU reached 19.79 g/L, the highest yield reported so far. The colanic acid produced by WQM003/pRAU was purified and its structure and physical properties were determined. This colanic acid shows a triple-helical structure and is stable up to 102 °C, and its melting temperature is 253.9 °C. This colanic acid shows a sphere-like chain conformation in aqueous solution. The viscosity of this colanic acid solution is related to concentration, shear rate, salt, temperature, and pH. At high concentrations, this colanic acid shows both viscous and elastic behaviors. These results suggest that the colanic acid produced by WQM003/pRAU has broad application prospects.