Exopolysaccharides (EPS) derived from lactic acid bacteria (LAB) possess notable physiological properties, including antioxidant, anti-tumor, immune-modulatory, and gastrointestinal regulatory activities, as well as heavy metal adsorption capacity, underscoring their broad application potential. The study aimed to screen high-EPS-yielding LAB from over 120 strains using a high-throughput strategy based on colony stringing and polysaccharide content. The isolated EPS was purified, structurally characterized, and investigated its cadmium (Cd) adsorption capacity and protective effects against Cd-induced toxicity in intestinal epithelial cells.

A novel acidic EPS, designated MY-5-EPS, was obtained from edible Lactococcus lactis MY-5 via DEAE anion-exchange and gel-permeation chromatography. With a molecular weight of 47.9 kDa, MY-5-EPS is composed of arabinose, galactose, glucose, xylose, and mannose in a molar ratio of 0.38:0.83:1:0.58:2.2. Structural analysis revealed predominant glycosidic linkages including →3,6)-α-Manp-(1→, →5)-α-Araf-(1→, →4)-α-Glcp-(1→, →2,6)-α-Galp-(1→, →4)-α-Manp-(1→, →4)-β-Glcp-(1→, and β-T-Glcp-(1→. The EPS demonstrated significant antioxidant activity, enhanced thermal stability, and excellent Cd adsorption capacity, with its microstructure and adsorption characteristics confirmed by SEM, EDS, and FT-IR.

In Caco-2 cells experiment, MY-5-EPS treatment significantly promoted cell growth and restored viability. Its cytoprotective effect against Cd toxicity operates through multiple pathways: suppressing apoptosis, attenuating oxidative stress, modulating inflammatory cytokines (IL-1β, TNF-α, IL-8, IL-6, IL-10), and preserving tight junction integrity by regulating the mRNA expression of Claudin-1, Occludin, and ZO-1. These multifunctional properties —Cd chelation, antioxidant, anti-inflammatory, and epithelial barrier preservation — established MY-5-EPS as a promising biochelator for heavy metal detoxification.