Structural Analysis of Enzyme-Resistant Isomaltooligosaccharides Reveals the Elongation of α-(1→3)-Linked Branches in Weissella confusa Dextran

Abstract

Weissella confusa VTT E-90392 is an efficient producer of a dextran that is mainly composed of α-(1→6)-linked D-glucosyl units and very few α-(1→3) branch linkages. A mixture of the Chaetomium erraticum endodextranase and the Aspergillus niger α-glucosidase was used to hydrolyze W. confusa dextran to glucose and a set of enzyme-resistant isomaltooligosaccharides. Two of the oligosaccharides (tetra- and hexasaccharide) were isolated in pure form and their structures elucidated. The tetrasaccharide had a nonreducing end terminal α-(1→3)-linked glucosyl unit (α-D-Glcp-(1→3)-α-D-Glcp-(1→6)-α-D-Glcp-(1→6)-α-D-Glc), whereas the hexasaccharide had an α-(1→3)-linked isomaltosyl side group (α-D-Glcp-(1→6)[α-D-Glcp-(1→6)-α-D-Glcp-(1→3)]-α-D-Glcp-(1→6)-α-D-Glcp-(1→6)-α-D-Glc). A mixture of two isomeric oligosaccharides was also obtained in the pentasaccharide fraction, which were identified as (α-D-Glcp-(1→6)-α-D-Glcp-(1→3)-α-D-Glcp-(1→6)-α-D-Glcp-(1→6)-α-D-Glc) and (α-D-Glcp-(1→6)[α-D-Glcp-(1→3)]-α-D-Glcp-(1→6)-α-D-Glcp-(1→6)-α-D-Glc). The structures of the oligosaccharides indicated that W. confusa dextran contains both terminal and elongated α-(1→3)-branches. This is the first report evidencing the presence of elongated branches in W. confusa dextran. The (1)H and (13)C NMR spectroscopic data on the enzyme-resistant isomaltooligosaccharides with α-(1→3)-linked glucosyl and isomaltosyl groups are published here for the first time.

Enzyme‐resistant isomalto‐oligosaccharides produced from Leuconostoc mesenteroides NRRL B‐1426 dextran hydrolysis for functional food application

“…The anomeric signals at 5.24 and 4.68 ppm were assigned to α and β (Rα H1 and Rβ H1) anomers, respectively, of α‐(1→6) linked glucosyl residue of the reducing end. The anomeric signal of 3‐ O ‐mono‐ and di‐substituted α‐(1→6) linked and α‐(1→3) linked glucosyl residues (in different environments) were observed in narrow regions of 4.99–4.97 ppm and 5.32–5.35 ppm, respectively, as also reported earlier . In general, dextranase hydrolyzed only long α‐(1→6) linkages, leaving at most two α‐(1→3) linked glucosyl residues at branch point.…”

“…In general, dextranase hydrolyzed only long α‐(1→6) linkages, leaving at most two α‐(1→3) linked glucosyl residues at branch point. The α‐glucosidase was reported to hydrolyze IMO2 and IMO3 into glucose residues . The enzyme‐resistant nature of IMO2 and IMO3 from L. mesenteroides NRRL B‐1426 was contrary to the recently reported IMOs produced from dextran of Weissella confusa VTT E‐90392 , L. mesenteroides NRRL B‐512F , and W. confusa Cab3 .…”

“…The α‐glucosidase was reported to hydrolyze IMO2 and IMO3 into glucose residues . The enzyme‐resistant nature of IMO2 and IMO3 from L. mesenteroides NRRL B‐1426 was contrary to the recently reported IMOs produced from dextran of Weissella confusa VTT E‐90392 , L. mesenteroides NRRL B‐512F , and W. confusa Cab3 . The dextran from L. mesenteroides NRRL B‐512F, W. confusa VTT E‐90392, and W. confusa Cab3 contained 5% , 3.5% , and 3% of α‐(1→3) branched linkages, respectively.…”

Cloning and Characterization of a Weissella confusa Dextransucrase and Its Application in High Fibre Baking

“…In the present study, the dextransucrase gene from W. confusa VTT E-90392 was identified and cloned. The strain performs well in wheat sourdough baking and its dextran structure is well-characterized [ 3 , 7 , 17 ]. In addition to the in silico analysis of the native dextransucrase WcE392-DSR, biochemical characterization of the recombinant enzyme (WcE392-rDSR) and its dextran product was carried out.…”

Synthesis of novel α-glucans with potential health benefits through controlled glucose release in the human gastrointestinal tract

“…Dextrans are approved as GRAS ingredients for their use in food products and feed. Also, the European Commission approves the use of dextran in baked goods at levels up to 5%; dextrans of high molecular weight are used in sourdough baking to produce good quality bread (SCO 2000;Maina et al 2011). Furthermore, dextran was described as a thickening agent, an alternative cryostabilizer, fat replacer, or low-calorie bulking agent of interest for the food processing industry (Park and Khan 2009).…”