Reprogramming the Metabolic Network in Kluyveromyces lactis with a Transcriptional Switch for De Novo Lacto- N -biose Synthesis.

Lacto--biose (LNB) is a member of the human milk oligosaccharide (HMO) family and is synthesized via an enzymatic reaction in vitro with -acetylglucosamine (GlcNAc) and cofactors. In this study, LNB was synthesized using a cell factory for the first time. First, three modules were constructed in for producing LNB from lactose and GlcNAc without the addition of cofactors. Second, a de novo pathway was constructed in for producing LNB from lactose without adding GlcNAc. Finally, a transcriptional switch was introduced into to reprogram its metabolic network for improving the flux from GlcNAc-6-P to GlcNAc in the de novo pathway. Subsequently, a final LNB yield of 10.41 g/L, similar to the salvage pathway yield, was achieved through the de novo pathway. The engineered provides a promising technology platform for the industrial scale production of LNB.