In VitroFermentation of Linear and α-1,2-Branched Dextrans by the Human Fecal Microbiota

Abstract

The role of structure and molecular weight in fermentation selectivity in linear ␣-1,6 dextrans and dextrans with ␣-1,2 branching was investigated. Fermentation by gut bacteria was determined in anaerobic, pH-controlled fecal batch cultures after 36 h. Inulin (1%, wt/vol), which is a known prebiotic, was used as a control. Samples were obtained at 0, 10, 24, and 36 h of fermentation for bacterial enumeration by fluorescent in situ hybridization and short-chain fatty acid analyses. The gas production of the substrate fermentation was investigated in non-pHcontrolled, fecal batch culture tubes after 36 h. Linear and branched 1-kDa dextrans produced significant increases in Bifidobacterium populations. The degree of ␣-1,2 branching did not influence the Bifidobacterium populations; however, ␣-1,2 branching increased the dietary fiber content, implying a decrease in digestibility. Other measured bacteria were unaffected by the test substrates except for the Bacteroides-Prevotella group, the growth levels of which were increased on inulin and 6-and 70-kDa dextrans, and the Faecalibacterium prausnitzii group, the growth levels of which were decreased on inulin and 1-kDa dextrans. A considerable increase in short-chain fatty acid concentration was measured following the fermentation of all dextrans and inulin. Gas production rates were similar among all dextrans tested but were significantly slower than that for inulin. The linear 1-kDa dextran produced lower total gas and shorter time to attain maximal gas production compared to those of the 70-kDa dextran (branched) and inulin. These findings indicate that dextrans induce a selective effect on the gut flora, short-chain fatty acids, and gas production depending on their length.

Functional and Structural Characterization of α-(1→2) Branching Sucrase Derived from DSR-E Glucansucrase

“…In addition, experimental conditions have been established that enable the production of new dextrans with controlled sizes and ␣-(132) linkage contents (12). The presence of ␣-(132) linkages renders these products resistant to the action of mammalian digestive enzymes and promotes the growth of beneficial bacteria of the gut microbiome (13)(14)(15)(16)(17).…”

Simultaneous synthesis of mixtures of lactulose and galacto-oligosaccharides and their selective fermentation

“…At 0, 4, 8 and 24 h of fermentation, 375 L samples were removed from the fermenters and added to 1.125 mL of filtered 4% (w/v) paraformaldehyde solution pH 7.2, mixed and stored at 4 • C for 6 h to fix the cells. Hybridization of the samples was carried out Faecalibacterium prausnitzii and relatives Hold et al (2003) as described by Sarbini et al (2011), using the appropriate genus specific 16 rRNA-targeted oligonucleotide probes labelled with the fluorescent dye Cy3 for the different target bacterial groups or the nucleic acid stain 4 ,6-diamidino-2-phenylindole (DAPI) for total cell counts ( Table 1). The bacterial groups studied were chosen as representative of the most numerically predominant and functionally relevant in the human colon.…”

Potential anti-obesogenic properties of non-digestible carbohydrates: specific focus on resistant dextrin

“…The type of linkages in the NDC also appears to affect the rate of fermentation. NDC with more 1 6 linkages relative to 1 4 linkages are more slowly fermented in the gastrointestinal tract (90) . Accordingly, NDC with a high number of 1 4 linkages and large monosaccharide chain lengths, such as resistant dextrin, long chain AXOS/arabinoxylans and long-chain inulin, may be more slowly fermented and reach more distal regions of the gastrointestinal tract for bacterial fermentation, whereas FOS for example may be fermented primarily in proximal regions of the gastrointestinal tract.…”