Overproduction of Exopolysaccharide Colanic Acid by Escherichia coli by Strain Engineering and Media Optimization.

Colanic acid (CA) is one of the major bacterial exopolysaccharides. Due to its biological activities, CA has a significant commercial value. However, the cultivation conditions have not been optimized for the large-scale production of CA. Here, we constructed a CA-overproducing Escherichia coli strain (ΔwaaF) and statistically optimized its culture media for maximum CA production. Glucose and tryptone were found the optimal carbon and nitrogen sources, respectively. Fractional factorial design indicated tryptone and Na2HPO4 as the critical nutrients for CA production. Through further optimization, we achieved a maximum CA production of 1910.0 mg/L, which is approximately 12-fold higher than the amount obtained using the non-optimized medium initially used. The predicted value of CA production was comparable with experimental value (2052.8 mg/L) under the optimized conditions. This study constitutes a successful demonstration of media optimization for increased CA production, and paves the way for future research for achieving large-scale CA production.