Increased Production of Colanic Acid by an Engineered Escherichia coli Strain, Mediated by Genetic and Environmental Perturbations

Colanic acid (CA) is a major exopolysaccharide synthesized by Escherichia coli that serves as a constituent of biofilm matrices. CA demonstrates potential applications in the food, cosmetics, and pharmaceutical industry. Moreover, L-fucose, a monomeric constituent of CA, exhibits various physiological activities, such as antitumor, anti-inflammatory, and skin-whitening. Here, the effects of genetic and environmental perturbations were investigated for improving CA production by E. coli. When rcsF, a positive regulator gene of CA synthesis, was expressed in E. coli Delta waaF, a CA-producing strain constructed previously, the CA titer increased to 3051.2 mg/L as compared to 2052.8 mg/L observed with E. coli Delta waaF. Among the environmental factors tested, namely, osmotic and oxidative stresses and pH, pH was a primary factor that significantly improved CA production. When the pH of the culture medium of E. coli Delta waaF + rcsF was maintained at 7, the CA titer significantly increased to 4351.6 mg/L. The CA yield obtained with E. coli Delta waaF + rcsF grown at pH 7 was 5180.4 mg CA/g dry cell weight, which is the highest yield of CA reported so far. This engineered E. coli system with optimization of environmental conditions can be employed for fast and economically-feasible production of CA.