Influence of in vitro pectin fermentation on the human fecal microbiome and O-glycosylation of HT29-MTX cells

Pectin is a structurally complex heteropolysaccharide that affects intestinal microorganisms and mucin O -glycans. The present study employed an in vitro model to investigate dynamic changes in microbiota during pectin fermentation. Residual pectin fragments arising from its fermentation were applied to HT29-MTX cells to study the effect of pectin structure on mucin O -glycosylation. Prevotella , Bacteroides , and Parabacteroides were found to preferentially degrade galactose, arabinose, and on the rhamnogalacturonan RG-I side chain region and methyl esterification groups of pectin. Bifidobacterium , Enterococcus , Megamonas , and Dorea metabolized the galacturonic HG region on pectin to produce butyrate. All pectin fragments were found to up-regulate total O -glycans (1.55–2.73 fold) and neutral O -glycans (1.11–1.49 fold) on HT29-MTX mucins. The large HG fragment (81.04 kDa) increased significantly the amount of non-fucosylated glycans (by 2.46-fold); whereas the small HG fragment (16.02 kDa) promoted fucosylated (by 9.25 fold), and especially di-fucosylated O -glycans. Collectively, these results demonstrate that gut microorganisms degrade pectin fragments in the following order of utilization: RG-I, RG-II, and HG. The small fragment of HG improves the expression of fucosylated O -glycans in HT29-MTX cells, mainly owing to an increase in di-fucosylated O -glycans.