Valorization of soybean seed coat pectic fibers as functional food hydrocolloids with anti-obesity activity

ABSTRACT Soybean seed coats (episperm) are an underutilized byproduct of soybean processing and represent a potential source of pectin-rich dietary fibers. In this study, black soybean seed coat (BSC), yellow soybean seed coat (YSC), and their dietary fiber (DF)-enriched fractions (BSCF and YSCF) were characterized for chemical composition and evaluated for their effects on high-fat diet (HFD)-induced obesity in mice. Monosaccharide composition analysis showed that all samples were dominated by arabinose-, galactose-, rhamnose-, and galacturonic acid–containing polysaccharides, indicating the presence of pectin-like structures rich in rhamnogalacturonan-I domains. Dietary supplementation with soybean seed coat preparations significantly attenuated HFD-induced body weight gain, adiposity, and hepatic steatosis, with BSCF showing the most pronounced effects. Improvements in serum lipid and glucose parameters were accompanied by modulation of hepatic genes related to inflammation and lipid metabolism. Histological analysis confirmed reduced lipid accumulation in liver and adipose tissues. In addition, soybean seed coat supplementation increased gut microbial α-diversity, altered overall microbial community structure, reduced the abundance of inflammation-associated phyla, and modulated several obesity-related genera. Correlation analysis further revealed associations between inflammatory cytokines, lipid metabolism–related genes, and gut microbiota. Overall, these results demonstrate that soybean seed coats, particularly their DF-enriched fractions, are a promising source of pectin-rich hydrocolloids with potential applications in functional foods targeting obesity and metabolic disorders