17 The digestibility of isomalto-oligosaccharides (IMO) as well as their metabolism by gut microbiota 18 depends on the degree of polymerization and the ratio of α-(1→4) to α-(1→6) linkages. Both 19 parameters are influenced by the method of production. Commercial IMO are produced by 20 transglycosylation of starch hydrolysates, or by transglycosylation with dextransucrase and 21 sucrose as glucosyl-donor and maltose as glucosyl-acceptor. This study aimed to quantitatively 22 and qualitatively

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... ssess the acceptor reaction with dextransucrase. α-Glucans were selected by 23 systematic variation of degree of polymerization and linkage type; the dextransucrase DsrM from 24 Weissella cibaria 10M was used as biocatalyst. The efficiency of α-glucans as acceptor 25 carbohydrates decreased in the order DP2 > DP3 > DP1; among disaccharides, the efficiency 26 decreased in the order α-(1→6) > α-(1→4) > α-(1→3); the α-(1→2) linked kojibiose did not 27 support oligosaccharide formation. Equimolar addition of efficient acceptor molecules and sucrose 28 shifted the dextransucrase reaction to oligosaccharides as virtually exclusive product. DsrM 29 readily extended a commercial IMO preparation by adding α-(1→6)-linked glucose moieties. 30 Conversion of commercial IMO by dextransucrase reduced their in vitro digestibility as analysed 31 by two different protocols. This study facilitates the synthesis of oligosaccharides produced in the 32 acceptor reaction with dextransucrase with controlled yields and degree of polymerization, and 33 hence with optimal functional properties in food applications. 34 Keywords. Dextransucrase, dextran, isomalto-oligosaccharides, panose, isomaltose, prebiotic, in 35 vitro digestibility. 36 37 Highlights 38  α-Glucans are efficient acceptor carbohydrates for dextransucrase DrsM. 39  The efficiency of acceptors for DsrM decreased in the order DP2 > DP3 > DP1 40  Among disaccharides, the efficiency decreased α-(1→6) > α-(1→4) > α-(1→3) 41  Equimolar addition of isomaltose and sucrose yielded only oligosaccharides. 42  Conversion of commercial IMO by dextransucrase reduced their in vitro digestibility 43 44 * *