The invention provides compositions and methods for engineering E. coli or other host production bacterial strains to produce fucosylated oligosaccharides, and the use thereof in the prevention or treatment of infection.

The present disclosure relates to improved strains for the production of Human Milk Oligosaccharides (HMOs) in large scale. The strains are genetically engineered to produce less acetate and/or ethanol during large-scale fermentation, in particular when encountering gradients with excess carbon source in the fermenter.

The present disclosure relates to the production of oligosaccharides, especially Human milk Oligosaccharides (HMOs) using a genetically engineered cell which has decreased or total loss of function of phosphoglycerol transferase I and II and/or phosphoethanolamine transferase and/or glucans biosynthesis protein C to reduce oligosaccharide by-products and/or increase oligosaccharide production.