Structural characterization, antioxidant activities and physicochemical properties analysis of a galactose-rich exopolysaccharide produced by Limosilactobacillus fermentum YL-11

Lactobacilli-derived exopolysaccharides (EPSs) are widely regarded as safe and has been employed as potential natural, non-toxic additives and functional agents in food industry. The structural properties of a galactose-rich exopolysaccharide produced by Limosilactobacillus fermentum YL-11 (YL-11 EPS) were investigated with chemical and instrumental analysis. The YL-11 EPS was determined to have a molecular weight (Mw) of 13.2 kDa. Nine different types of glycosidic bonds were identified in YL-11 EPS. The inferred structure of the YL-11 EPS contained the backbone of →2)-β-D-Galp-(1→[3)-β-D-Galp-(1] 4 →3)-β-D-Galp-(1→3)-β-D-Galp-(1→, with two side chains, β-D-Galp-(1→6)-α-D-Manp-(1→6)-[α-D-Glcp-1→2]-α-D-Manp-(1→3)-[α-D-Glcp-1→6]-α-D-Glcp-(1→3)-[α-D-Glcp-1→6]-α-D-Glcp-(1→ with an acetyl group at the O-3 position of →2,6-α-D-Manp-1→ and α-L-Araf-(1→, which were present at the C6 location of the 1,3-β-D-Galp. The YL-11 EPS showed concentration-dependent antioxidant activities and the DPPH, ABTS, hydroxyl groups and superoxide radicals scavenging rates of 10 mg/mL YL-11 EPS reached 61%, 74%, 35.4% and 40%, respectively. The YL-11 EPS also has a beneficial protective impact on H 2 O 2 -injured cells, which pretreatment with YL-11 EPS can substantially decrease ROS levels and enhance SOD enzyme activity. Additionally, the YL-11 EPS exhibited good thickening properties and thermal stability. The EPS’s structural information and physicochemical properties provide a basis for studying their structure-function relationships. • The structure of a galactose-rich EPS from L. fermentum YL-11 were characterized. • The galactose-rich YL-11 EPS exhibited potent antioxidant activities in vitro. • The YL-11 EPS exhibited good thickening properties and thermostability.