Gut-Protective and Multifunctional Exopolysaccharide from Enterococcus faecium HDRsEf1: Structural Characterization and Protective Effects Against Enteropathogenic E. coli-Induced Intestinal Inflammation

Abstract

Background: Enteropathogenic Escherichia coli (EPEC) disrupts intestinal barrier integrity by adhering to epithelial cells, leading to diarrhea, impaired nutrient absorption, oxidative stress, and intestinal inflammation in young animals. This study aimed to isolate and characterize a neutral exopolysaccharide (EPS-T1) from Enterococcus faecium HDRsEf1, evaluate its functional activities in vitro, and assess its protective effects against EPEC-induced enteritis in vivo. Results: EPS-T1, with a molecular weight of 81.21 ± 1.28 kDa, was mainly composed of glucose, galactose, rhamnose, and mannose, and exhibited a porous, sheet structure with relatively high thermal stability. In vitro, EPS-T1 (200 μg/mL) significantly inhibited EPEC growth and biofilm formation, reduced bacterial adhesion to intestinal epithelial cells, and exhibited broad-spectrum free radical scavenging activity. In vivo, EPS-T1 treatment alleviated EPEC-induced weight loss and intestinal tissue damage, reduced the intestinal EPEC load, downregulated pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6), upregulated the anti-inflammatory cytokine IL-10, and improved serum antioxidant indices (T-AOC, SOD, and GSH-PX) while decreasing MDA levels. Conclusions: These results demonstrate that EPS-T1 derived from Enterococcus effectively mitigates EPEC-induced intestinal inflammation and oxidative stress, highlighting its potential as an immunobiotic functional candidate.