Isolation and characterization of a novel exopolysaccharide from the fermented probiotic Lactiplantibacillus plantarum ZZU-1 and its application for attenuating autism-like behaviors.

Lactic acid bacteria-derived exopolysaccharides (EPS) are natural and safe functional biomolecules whose antioxidant potential is largely dependent on their specific chemical structures. Accumulating evidence suggests that LAB-EPS may exert indirect regulatory effects on oxidative stress-related diseases like autism spectrum disorder via modulating intestinal microecology and relieving oxidative stress in the gut-brain axis. In this study, a novel EPS (EPS-ZZU) was isolated from Lactiplantibacillus plantarum ZZU-1 of traditional fermented Suancai. Structural characterization revealed a 2.141 kDa molecular weight, with mannose, glucose and ribose in a 34.40:26.35:12.24 molar ratio, composed of α-configuration pyranose units. EPS-ZZU exhibited over 90% scavenging rates against the typical free radicals, including hydroxyl radical (⋅OH), 1,1-diphenyl-2-picrylhydrazyl radical (DPPH•), superoxide anion (O2 •⁣-) and 2,2'-azinobis (3-ethylbenzothiazoline-6-sulfonate) cation radical (ABTS•+) at a concentration of 5 mg/mL, which was comparable to that of vitamin C (Vc). In a one-month mouse trial, EPS-ZZU significantly alleviated autism-like behaviors (social deficits, repetitive actions) by reducing oxidative stress and inflammation, enhancing intestinal barrier integrity, and reshaping gut microbiota-enriching beneficial taxa (Adlercreutzia, Christensenellaceae) and inhibiting pathogens (Erysipelatoclostridium). Metabolomics confirmed upregulated indole-3-acetate and downregulated cognitive impairment-associated metabolites (asymmetric dimethylarginine, homogentisic acid). These findings highlight EPS-ZZU's therapeutic potential for autism and provide a new idea for developing more bioactive bacterial EPS antioxidants.