Regulation on Pathway Metabolic Fluxes to Enhance Colanic Acid Production in Escherichia coli

Colanic acid (CA) is a natural polysaccharide macromolecule with rich and unique biological properties and is a promising candidate for use in food and cosmetics. To date, the efficient biosynthesis of CA and the influence of product accumulation on the strains used have yet to be precisely investigated. Herein, bottlenecks in the CA metabolic pathway were untangled by finely regulating the expression of manA, cpsG, fcl, and rcsA. Engineered strains produced CA at >1 g/L in shake flasks without dependence on cold temperatures, and it was verified in a 1 L bioreactor with a titer up to 18.64 g/L within 24 h. The accumulation of CA caused a decrease in the saturated fatty acid content (represented by C_16:0 and C_18:0) in the cell membrane. This study demonstrated pathway engineering for efficient CA production in cell factories and provided insights into the barriers and solutions faced in the biosynthesis of natural products.