Effect of highly branched α-glucans synthesized by dual glycosyltransferases on the glucose release rate

Abstract

Increasing α-1,6 linkages in starch molecules generates a large amount of α-limit dextrins (α-LDx) during α-amylolysis, which decelerate the release of glucose at the intestinal α-glucosidase level. This study synthesized highly branched α-glucans from sucrose using Neisseria polysaccharea amylosucrase and Rhodothermus obamensis glycogen branching enzyme to enhance those of slowly digestible property. The synthesized α-glucans (Mw: 1.7–4.9 × 107 g mol−1) were mainly composed of α-1,4 linkages and large proportions of α-1,6 linkages (7.5%–9.9%). After treating the enzymatically synthesized α-glucans with the human α-amylase, the quantity of branched α-LDx (36.2%–46.7%) observed was higher than that for amylopectin (26.8%) and oyster glycogen (29.1%). When the synthetic α-glucans were hydrolyzed by mammalin α-glucosidases, the glucose generation rate decreased because the amount of embedded branched α-LDx increased. Therefore, the macro-sized branched α-glucans with high α-LDx has the potential to be used as slowly digestible material to attenuate postprandial glycemic response. © 2021