Ultrasound-Assisted Extraction Modifies the Structural Characteristics and Enhances the Prebiotic Potential of Large Yellow Tea Polysaccharides

• Ultrasound-assisted extraction altered LYPS structure, enhancing its prebiotic potential. • LYPS-U had a lower molecular weight and more uniform morphology than LYPS-W. • Both LYPS samples resisted gastrointestinal digestion but were efficiently utilized by gut microbiota. • LYPS-U promoted higher production of short-chain fatty acids (SCFAs) during in vitro fermentation. • LYPS stimulated SCFA-producing bacteria including Bacteroides and Phascolarctobacterium and inhibited pathogens such as Pseudomonas . Large yellow tea polysaccharides (LYPS) have demonstrated various bioactivities, including antioxidant, lipid metabolism regulation, and hypoglycemic effects. However, their gastrointestinal digestibility and potential prebiotic functions remain largely unknown. This study aimed to compare the structural characteristics and in vitro fermentation behaviors of LYPS using traditional hot water extraction (LYPS-W) and ultrasound-assisted extraction (LYPS-U), with a focus on their potential prebiotic effects. Ultrasonic extraction significantly modified the structural features of LYPS, yielding a lower molecular weight and higher contents of galacturonic acid, along with more uniform particle morphology. Both LYPS-W and LYPS-U resisted upper gastrointestinal digestion but were readily fermented by gut microbiota. LYPS-U exhibited superior fermentability, producing significantly higher levels of short-chain fatty acids (SCFAs), particularly acetic and propionic acids, compared with LYPS-W. Microbial analysis revealed that both polysaccharides promoted the growth of beneficial SCFAs-producing bacteria, such as Bacteroides , Prevotellaceae_UCG-001 , and Phascolarctobacterium , and suppressed potential pathogens such as Pseudomonas . Thus, ultrasound-assisted extraction enhances the structural accessibility and biological functionality of LYPS, improving their microbial fermentability and prebiotic potential. These findings provide a theoretical foundation for the application of ultrasonic processing in the development of gut-targeted functional foods based on tea-derived polysaccharides.