Ultrasonic‑assisted extraction alters molecular structure and microbial fermentation characteristics of palm fruit...

The palm oil industry generates abundant by-products with great potential for high-value utilization. This study compared the yield, structural characteristics, and regulatory effects on β-carotene bioconversion of palm fruit polysaccharides obtained by conventional lactic-acid warm-water extraction (CE-PFP) and ultrasound-assisted extraction (UE-PFP). The yield of UE-PFP was 1.62 times that of CE-PFP, and UE-PFP exhibited lower molecular weight and altered monosaccharide composition. Methylation analysis and nuclear magnetic resonance spectroscopy demonstrated that ultrasonication reshaped the fine glycan architecture of palm‑fruit polysaccharides. Compared with CE‑PFP, UE‑PFP contained rhamnose residues within its backbone and lost glucose residues in its side‑chains, leading to substantial rearrangement of side‑chain sugar‑residue profiles. SEM further revealed distinct morphological disparities: CE‑PFP adopted a dense layered structure, whereas UE‑PFP possessed a loose porous fibrous network. Compared with CE‑PFP, UE‑PFP exhibited stronger inhibition against Escherichia coli and more pronounced enrichment of Bacteroides, showing superior overall capacity for gut‑microbiota remodeling. Meanwhile, UE‑PFP displayed greater potency in up‑regulating β‑carotene‑metabolizing enzymes and facilitating retinol synthesis. Pseudo‑germ‑free mouse assays confirmed that the β‑carotene‑to‑retinol bioconversion‑promoting effects of both CE‑PFP and UE‑PFP were dependent on gut‑microbiota remodeling. In summary, ultrasonic modification remodels the gut‑microbiota‑regulatory capacity of palm‑fruit polysaccharides, providing new insights into plant polysaccharide modification and the valorization of palm‑oil by‑products.