Macromolecular α-glucans with α-1,3/α-1,4 branching structures produced using dual glycosyltransferases: Elucidation of physicochemical and slowly digestible properties

Amylosucrase from Neisseria polysaccharea (NpAS) produces the linear amylose-like a-glucans by the elongation property from sucrose, and 4,3-a-glucanotransferase from Lactobacillus fermentum NCC 2970 (4,3-aGT) newly synthesizes the a-1,3 linkages after cleaving the a-1,4 linkages by the glycosyltransferring property. This study focused on the synthesis of high molecular a-1,3/a-1,4-linked glucans by combining NpAS and 4,3-aGT and analyzed their structural and digestive properties. The enzymatically synthesized a-glucans have a molecular weight of >1.6 x 107 g mol-1, and the a-4,3 branching ratios on the structures increased as the amount of 4,3-aGT increased. The synthesized a-glucans were hydrolyzed to linear maltooligosaccharides and a-4,3 branched a-limit dextrins (a-LDx) by human pancreatic a-amylase, and the amounts of produced a-LDx were increased depending on the ratio of synthesized a-1,3 linkages. In addition, approximately 80 % of the synthesized products were partially hydrolyzed by mammalian a-glucosidases, and the glucose generation rates decelerated as the amounts of a-1,3 linkages increased. In conclusion, new types of a-glucans with a-1,4 and a-1,3 linkages were successfully synthesized by a dual enzyme reaction. These can be utilized as slowly digestible and prebiotic ingredients in the gastrointestinal tract due to their novel linkage patterns and high molecular weights.

Automated summary

This study successfully synthesized new types of α-glucans with α-1,4 and α-1,3 linkages through a dual enzyme reaction. These glucans have novel linkage patterns and high molecular weights, and can be utilized as slowly digestible and prebiotic ingredients in the gastrointestinal tract.