Aureobasidium-mediated enzymatic depolymerization enhances the antioxidant capacity of citrus pectin

Four citrus pectins were extracted from different discarded citrus peels. PPG, CJ, and QC pectins presented degrees of esterification (DE) values that exceeded 80%; in contrast, WG pectin presented a notably lower DE, which was reduced to approximately 65%. All four pectins are composed of seven monosaccharides: galacturonic acid, arabinose, galactose, glucose, rhamnose, mannose, and xylose, with galacturonic acid emerging as the predominant constituent (more than 50%). The molecular weights (Mws) of the four pectins all exceeded 100 kDa. Two Aureobasidium strains (40 and 44), which were isolated from CWs, harboured genomes enriched with pectin-depolymerizing carbohydrate-active enzymes (CAZymes). Following temperature and pH optimization of the pectin-degrading enzyme systems in the two black yeast strains, both effectively depolymerized the four pectins into lower-Mw oligosaccharides. All four pectin oligosaccharide products exhibited significant radical scavenging capacities against DPPH, superoxide anion and hydroxyl radicals, demonstrating their effectiveness as natural free radical scavengers.

The online version contains supplementary material available at 10.1007/s10068-025-02023-6.