Extraction-Dependent Structural Diversity of White Kidney Bean Cotyledon Polysaccharides Determines Their Effects on Ex Vivo Fermentation of the Elderly Gut Microbiota.

Different extraction methods produced white kidney bean cotyledon polysaccharides with distinct monosaccharide compositions.

• Ultrasound-assisted acid extraction (WKBC-P1) and chelator extraction (WKBC-P3) produced polysaccharides rich in arabinose.
• Alkaline extraction (WKBC-P2) produced polysaccharides containing high levels of glucose.
• Three extraction methods were used: ultrasound-assisted acid (WKBC-P1), alkaline (WKBC-P2), and chelator (WKBC-P3).

Extraction method determined the molecular weight and structural uniformity of the resulting polysaccharide fractions.

• Acidic extraction led to smaller, more fragmented polysaccharides.
• Chelating extraction produced the highest molecular weight and most uniform fractions.
• Molecular weight analysis was used to characterize structural differences among the three fractions.

WKBC-P1 and WKBC-P2 significantly increased the relative abundance of beneficial gut bacteria in ex vivo fermentation with elderly gut microbiota.

• Both WKBC-P1 and WKBC-P2 significantly increased the relative abundance of Bifidobacterium and Bacteroides_H.
• Both fractions suppressed potentially harmful Proteobacteria.
• Ex vivo fermentation was performed using pooled fecal microbiota from elderly individuals aged 65–70 years old.
• WKBC-P3 (chelator extraction) did not show the same beneficial microbial effects as WKBC-P1 and WKBC-P2.

WKBC-P1 and WKBC-P2 fermentation induced robust production of short-chain fatty acids (SCFAs) while reducing branched short-chain fatty acids (bSCFAs).

• Both WKBC-P1 and WKBC-P2 induced robust production of short-chain fatty acids (SCFAs).
• Both fractions reduced branched short-chain fatty acids (bSCFAs).
• The reduction in bSCFAs indicates a metabolic shift toward carbohydrate fermentation rather than protein catabolism.
• This metabolic shift is considered beneficial for gut health in elderly populations.

Aging is associated with profound alterations in gut microbiota composition, reduced microbial diversity, and impaired metabolic resilience.

• Age-related gut microbiota disorders were the motivation for investigating dietary polysaccharides as potential interventions.
• Dietary polysaccharides with different structures exhibit varying efficacy in alleviating these age-related disorders.
• The study focused on elderly participants aged 65–70 years old as the source of fecal microbiota for fermentation experiments.

Acidic and alkaline extraction methods yielded polysaccharide fractions superior to chelator extraction for supporting beneficial microbial growth and SCFA generation in aging microbiota.

• WKBC-P1 (acid extraction) and WKBC-P2 (alkaline extraction) were identified as the most effective fractions.
• WKBC-P3 (chelator extraction), despite producing the highest molecular weight and most uniform fractions, did not demonstrate equivalent prebiotic effects.
• The findings suggest white kidney bean cotyledon polysaccharides are promising prebiotic candidates for maintaining gut homeostasis and metabolic health in elderly populations.