Impact of Tunisian Fermented Zgougou and Related Lactobacilli on Caco‐2 Cell Barrier Integrity: Upregulation of Key Tight Junction Proteins

The intestinal barrier is a critical regulator of gut health, often compromised by dysbiosis and inflammation. Given the rising interest in fermented plant-based foods and probiotics as adjuvants in maintaining gut health, this study explored the biological activity of zgougou juice, comparing spontaneous fermentation (J) with driven fermentation using two lactobacilli with probiotic traits (namely Lactiplantibacillus paraplantarum A1 and Lactiplantibacillus plantarum A2), as well as the effects of cell biomass and Cell-Free Supernatants (CFS) obtained from those lactobacilli. Using a Caco-2 cell monolayer model, we assessed barrier integrity via Transepithelial Electrical Resistance (TEER) and gene expression of Tight Junction Proteins (TJP) and the cytokine Tumor Necrosis Factor α (TNFα). Treatment of Caco-2 monolayer with zgougou juice fermented with lactobacilli significantly reinforced the intestinal barrier, with TEER values reaching 690–963.33 Ω·cm2. Furthermore, it upregulated TJP expression, outperforming bacterial biomass and their CFS. These findings would suggest that zgougou juice improves intestinal barrier, though further in vivo and clinical trials are necessary to claim any benefits for human health.