In vitro digestibility of the Sargassum fusiforme polysaccharide fermented using Lactobacillus acidophilus and its improving effect on intestinal inflammation in zebrafish

This study investigated the in vitro digestion characteristics of the Sargassum fusiforme polysaccharide fermented using Lactobacillus acidophilus (LA-rSFP) and its effects on dextran sulfate sodium-induced intestinal inflammation in zebrafish. The treatment substantially decreased the molecular weight of LA-rSFP and increased the reducing sugar content during gastrointestinal digestion. LA-rSFP considerably enhanced the activities of superoxide dismutase and catalase and markedly decreased malondialdehyde content, indicating a reduction in oxidative stress in the intestinal environment. Moreover, LA-rSFP ameliorated colitis-induced intestinal injury and upregulated the expression of tight junction proteins (occludin, ZO-1, and claudin-1), suggesting strengthened intestinal barrier integrity. LA-rSFP also played an important role in regulating pro-inflammatory cytokines (downregulated) and anti-inflammatory cytokines (upregulated) during inflammatory responses in the zebrafish gut. The results of 16S rRNA sequencing showed that LA-rSFP increased the diversity and richness of the intestinal microbiota in zebrafish with inflammatory bowel disease (IBD), enhancing the abundance of beneficial bacteria, such as Fusobacteria, Firmicutes, Bacteroidetes, and Lactobacillus, and reducing Proteobacteria levels. These findings suggest that the administration of LA-rSFP alleviates IBD, with the therapeutic mechanisms partially attributed to the regulation of the intestinal microbiota composition and abundance.