Microbial Utilization and Selectivity of Pectin Fractions with Various Structures

Abstract

To evaluate the fermentation properties of oligosaccharides derived from pectins and their parent polysaccharides, a 5-ml-working-volume, pH-and temperature-controlled fermentor was tested. Six pectic oligosaccharides representing specific substructures found within pectins were prepared. These consisted of oligogalacturonides (average degrees of polymerization [DP] of 5 and 9), methylated oligogalacturonides (average DP of 5), oligorhamnogalacturonides (average DP of 10 as a disaccharide unit of galacturonic acid and rhamnose), oligogalactosides (average DP of 5), and oligoarabinosides (average DP of 6). The influence of these carbohydrates on the human fecal microbiota was evaluated. Use of neutral sugar fractions resulted in an increase in Bifidobacterium populations and gave higher organic acid yields. The Bacteroides-Prevotella group significantly increased on all oligosaccharides except oligogalacturonides with an average DP of 5. The most selective substrates for bifidobacteria were arabinan, galactan, oligoarabinosides, and oligogalactosides.Pectins are complex plant heteropolysaccharides consisting in the main of four types of carbohydrate structure. These are partially methyl and/or acetyl esterified polygalacturonic acid (PGalA), rhamnogalacturonan type I (RG I), xylogalacturonan, and rhamnogalacturonan type II (RG II). PGalA is a linear homopolymer of ␣-(1,4)-galacturonic acid. Xylogalacturonan consists of a PGalA backbone with xylose bound to galactopyranosyluronic acid (GalpA) at C-3. RG I and RG II comprise the so-called "hairy regions" due to their branched structures. The -4-␣-D-GalAp-1,2-␣-L-Rhap-1-disaccharide sequence constitutes the main chain of RG I, with substitutions at position 4 of the rhamnose residues as well as acetylation on C-2 or C-3 of the galacturonic acid. Side chains are ␣-(1,5)-arabinan, ␤-(1,4)-galactan, and arabinogalactan type I. RG II is very complex, but it is believed to be the most conserved part of pectin. This molecule has PGalA as a backbone and is branched with rhamnose and other rare sugars such as apiose, 2-O-methylxylose, and 2-O-methylfucose (31).The biological effects of pectins have been studied extensively, and they are reported to be highly fermentable dietary fibers (5). Apart from their complexity and heterogeneity, both pectins and their derivatives have been investigated for many other potential health benefits. Pectins are found in oriental medicinal herbs and are thought to be responsible for their therapeutic effects (18,27). Studies to date indicate that different regions of pectins may mediate the different health effects. For example, modified citrus pectin may control the progress of malignancy (12) or induce apoptosis in cancer cell lines (20,29). In terms of the selectivity of fermentation by fecal bacteria, pectic oligosaccharides had greater selectivity toward bifidobacteria in batch cultures than the parent pectin (24,25,30).Many plant by-products are rich in pectins, which could possibly be sources of active pectic compounds and may prove ...

In Situ Prebiotics for Weaning Piglets: In Vitro Production and Fermentation of Potato Galacto-Rhamnogalacturonan

“…more galactan and half the galacturonic acid content, findings which suggest that the galactan chains of the molecule have a more pronounced effect on the genus Lactobacillus, whereas the galacturonic acid chains may be favored by bacteria belonging to the genus Clostridium. It has previously been shown that in human feces, pectin fractions with neutral sugars were efficient in increasing the amount of Bifidobacterium organisms, whereas the amount of Clostridium bacteria was increased by polygalacturonic acid, as enumerated by fluorescent in situ hybridization (FISH) (61). In contrast, another study using a pectin fraction with high levels of galacturonic acid also showed by means of FISH little growth of clostridia and increased levels of Bifidobacterium (62).…”

Ultrasonic Modification of Selected Polysaccharides-Review

“…Prebiotics, oligo pectins have been shown to be better prebiotics for specific probiotic bacteria like Bifidobacteria and Lactobacilli. The selectivity of oligosaccharide depend on the chain length and presence of specific functional groups, the oligo pectins with short chain being preferred substrate for probiotics [80,81].…”

The effect of modified citrus pectin-probiotic on faecal lactobacilli in Balb/c mice

“…Although, there was no significant difference in the number of faecal lactobacilli count between the MCP-treated mice and control (p > 0.05), the reduced faecal lactobacilli presented by MCP-treated mice corroborates the observation made by Doyle (2007), Biagi et al (2010) and Zhong et al (2014) that pectin stimulates bacteria other than lactic acid bacteria. Conversely, some studies showed that citrus pectin encourages the proliferation of lactobacillus species which is dependent on the composition and prebiotic index of the pectic fraction-arabinan and galactan (Dnumpai et al, 2011), degree of methylation and selective fermentation of pectin (Dlano-Martin et al, 2002).…”