Fermentation characteristics of pectin-derived oligosaccharides from enzyme treated side streams of citrus processing

This study explored the conversion of citrus juice side streams into fermentable oligosaccharides for potential gut health benefits. Alcohol washed, insoluble lemon peel waste was enzymatically treated using technical pectinolytic enzyme preparations, yielding mixtures of galactose- arabinose- and either methyl-esterified or non-methyl-esterified galacturonic acid oligosaccharides (OS) with a Δ4,5-unsaturated non-reducing end resulting in mixtures of pectin-derived OS: POS and POSNME. Both mixtures were completely fermented during in vitro batch fermentation by proximal and distal microbiota of three healthy adult donors. Fermentation by distal and proximal microbiota resulted in similar methyl-ester-dependent mechanisms of POS utilization, yielding health beneficial acetate, propionate and butyrate in significant amounts. Arabinose-, galactose- and non-methyl-esterified Δ4,5-unsaturated galacturonic acid OS were utilized significantly faster by the distal and proximal microbiota of donors 1 and 2 compared to methyl-esterified Δ4,5-unsaturated galacturonic acid OS, suggesting methyl-esterification of Δ4,5-unsaturated galacturonic acid oligosaccharides as a substantial regulator of POS fermentability. The findings presented in this manuscript suggest that carbohydrate molecular structure and availability, rather than microbiota composition, determine carbohydrate fermentation patterns along the colon, emphasizing that the consumption of differently fermentable fiber is essential to promote gut health along the colon.