Structural characterization of slow digestion dextrin synthesized by a combination of α-glucosidase and cyclodextrin glucosyltransferase and its prebiotic potential on the gut microbiota in vitro

•A soluble and stable slow digestion dextrin (SDD) was synthetized by α-glucosidase and CGTase.•SDD contained 62.4% α-1,6 bond and showed similar digestibility to commercial dietary fibers.•SDD markedly promoted Bifidobacterium in pure and mixed cultures of human gut bacteria.•SDD produced more organic acids (81.19 ± 5.71 mM) when fermented with human gut bacteria.