Extraction method shapes the structure and fermentation behavior of white kidney bean episperm polysaccharides in gut microbiota of the elderly

Aging is often accompanied by gut microbiota dysbiosis. Dietary supplementation with polysaccharides offers a promising, cost-effective approach to restore microbial balance and support healthy aging. This study investigated structural characteristics and in vitro fermentation behavior of white kidney bean episperm polysaccharides extracted using ultrasound-assisted acid (AEP), enzyme (EEP), and chelator (CEP) methods. Extraction method markedly influenced structure: AEP and CEP were enriched in xylose and arabinose, while EEP was rich in glucose and xylose. Morphologically, AEP exhibited a compact, porous structure. Fermentation profiles revealed that AEP notably enriched Bifidobacterium and produced the highest levels of butyric acid. Xylose in AEP supported sustained carbohydrate availability throughout fermentation, while CEP was rapidly degraded. All fractions increased total SCFAs and reduced bSCFAs. These findings suggest that white kidney bean episperm polysaccharides, particularly AEP, have strong prebiotic potential for modulating elderly gut microbiota and may serve as a promising ingredient targeting age-related microbial dysbiosis.