Engineering the substrate transport and cofactor regeneration systems for enhancing 2’-fucosyllactose synthesis in Bacillus subtilis

Human milk oligosaccharides (HMOs) have been proven to be beneficial to infants’ intestinal health and immune systems. 2′-Fucosyllactose (2′-FL) is the most abundant and thoroughly studied HMO and has been approved to be an additive of infant formula. How to construct efficient and safe microbial cell factories for the production of 2′-FL attracts increasing attention. In this work, we engineered the Bacillus subtilis as an efficient 2′-FL producer by engineering the substrate transport and cofactor guanosine 5′-triphosphate (GTP) regeneration systems. First, we constructed a synthesis pathway for the 2′-FL precursor guanosine 5′-diphosphate-l-fucose (GDP-l-fucose) by introducing the salvage pathway gene fkp from Bacteriodes fragilis and improved the fucose importation by overexpressing the transporters. Then, the complete synthesis pathway of 2′-FL was constructed by introducing the heterologous fucosyltransferases from different sources, and it was found that the gene from Helicobacter pylori was the be...