Ultrasonic Degradation Improves the In Vitro Utilization of Oolong Tea Pectic Polysaccharides: Structure Characterization and Multi-Omics Insights

Abstract

Pectic polysaccharides from tea residues represent a promising class of prebiotic dietary fibers. This study aimed to optimize the extraction of Oolong tea (Camellia sinensis ‘Foshou’) polysaccharides (FCTP), elucidate the structural alterations induced by ultrasonic degradation, and evaluate the consequent in vitro utilization using Lactobacillus salivarius BXP5. Enzyme-assisted extraction significantly improved the yield of FCTP to 11.10%, compared to 6.74% via conventional hot-water extraction. Ultrasonic treatment (120–240 W, 20–45 min) reduced the molecular weight (Mw) from 1079.9 kDa to 690.7–824.4 kDa, increased the uronic acid content, disrupted the triple-helix conformation, and transformed the polysaccharide into a looser and more water-accessible structure. Structural characterization by FTIR, methylation, and NMR further indicated that uFCTP remained an acidic pectic polysaccharide enriched in homogalacturonan (HG)-like domains. In vitro fermentation demonstrated that ultrasonically degraded FCTP (uFCTP) more effectively promoted BXP5 proliferation than native FCTP. Non-targeted metabolomics and proteomics revealed that uFCTP exerted more pronounced regulatory effects on nucleotide metabolism, carbon metabolism, and ribosomal biogenesis. Correlation analysis identified key metabolites (e.g., gallic acid, xanthosine monophosphate) tightly associated with differentially expressed proteins involved in carbohydrate utilization and cellular growth. These findings indicate that ultrasonic degradation is an effective physical modification strategy to improve utilization by L. salivarius BXP5 of tea-derived pectic polysaccharides by tailoring their molecular architecture for improved probiotic fermentation and metabolic cross-talk.