Arabinose side-chains play a crucial role in fermentation properties of RG-I enriched citrus pectin

The relationship between pectin side chains and fermentability is crucial for understanding precision nutrition. In this study, α-L-arabinofuranosidase and β-galactosidase were used to remove arabinose and galactose side chains of citrus pectin. Effects of RG-I side chains on structural characteristics and in vitro fermentation property of pectin were investigated. The removal of arabinose and galactose side chains led to a decrease in molecular weight and branching degree of pectin, which in turn resulted in a loose spatial conformation. Based on correlation analysis and carbohydrate-active enzymes annotation, we concluded that the presence of arabinose in citrus pectin promoted the production of propionate and had no promoting effect on the proliferation of pathogenic bacteria of Escherichia and Klebsiella . The removal of the galactose side chain promoted proliferation of potentially beneficial bacteria ( Bifidobacterium , Faecalibacterium , Veillonella , and Parabacteroides ). We further found that arabinose produced propionate mainly via the succinate pathway and acrylate pathway, while galactose generated butyrate by activating phosphate butyryltransferase and butyrate kinase. Our results provide new insights into structure-function relationship between arabinose and galactose side chains and fermentability of pectin, while also offering a scientific reference for targeted design of pectin prebiotics with precise functionalities.