Production of tailor-made α-glucans with enhanced α-1,6 linkage ratio via a bottom-up approach to modulate...

Carbohydrates enriched in α-1,6 linkages are digested more slowly in the gastrointestinal tract due to the low hydrolytic activity of isomaltase, a key small intestinal α-glucosidase. In this study, we employed a bottom-up enzymatic approach to synthesize tailor-made α-glucans with controlled α-1,6 linkage ratios and molecular sizes from sucrose, a highly water-soluble substrate that does not require energy-intensive gelatinization, unlike conventional starch-based substrates typically used for enzymatic modification. This was achieved using a dual-enzyme system composed of amylosucrase from Neisseria polysaccharea and 4,6-α-glucanotransferase from Streptococcus thermophilus strain NCC2408. The resulting α-glucans exhibited molecular weights ranging from 2.6 × 10³ to 1.2 × 10⁴ Da and showed significant increases in α-1,6 linkage content (14.2-23.5 %) and embedded α-limit dextrin fractions (48.9-69.2 %) as St4,6-αGT concentrations increased. These structural modifications resulted in slower hydrolysis by mammalian α-glucosidases in vitro, and significantly (p < 0.05) attenuated initial blood glucose levels in a mouse model compared to glucose controls. These findings demonstrate that α-glucans synthesized via this bottom-up enzymatic method possess slow digestibility and prolonged glycemic responses. Therefore, they hold strong potential as functional carbohydrate ingredients for regulating glucose homeostasis and providing sustained energy, contributing to strategies for managing obesity and type 2 diabetes.