Production of human milk oligosaccharides in microbial hosts with engineered import/export

A method for production of an oligosaccharide comprising a lacto-N-triose II (LNT-II;

• GlcNAc(β1-3)Gal(β1-4)Gluc) as a core trisaccharide by a genetically modified microbial host cell, comprising
• providing a genetically modified microbial host cell that comprises:
• at least one recombinant glycosyltransferase;
• increased expression or activity of at least one endogenous sugar export protein capable of exporting the oligosaccharide;
• and
• decreased expression or inactivation of at least one export protein that exports precursors of the oligosaccharide from the host cell;
• cultivating the host cell in a medium under conditions permissive for the production of the oligosaccharide, whereby the oligosaccharide is exported into the medium at an increased level compared to the unmodified host cell, and
• obtaining the oligosaccharide from the medium.