| Summary: | Maintaining probiotic effectiveness represents the most important task for the development of functional foods. Gastrointestinal stability and intestinal adhesion properties comprise one criterion for probiotic selection. Here, we investigated the benefits of milk fermented with <i>Lactobacillus casei</i> HY2782 at different fermentation times. The probiotic strain used was <i>L. casei</i> HY2782 and the reference strain was <i>L. casei</i> ATCC393 for comparisons. The samples were fermented for 7 days at 30 °C. We determined the pH, CFU/mL, survival rate during simulated gastrointestinal digestion, adhesion ability to HT-29 cells, and gene expression of tight-junction proteins known to regulate intestinal permeability in Caco-2 cells. <i>L. casei</i> HY2782 exhibited significantly higher survival rates in simulated gastrointestinal digestion during long-term fermentation than <i>L. casei</i> ATCC393. The adhesion ability to HT-29 cells was significantly increased with <i>L. casei</i> HY2782 (3.3% to 8.7%) after 7 days of fermentation; however, only a slight increase was observed for <i>L. casei</i> ATCC393 (3.1% to 4.7%). In addition, <i>L. casei</i> HY2782 can significantly increase the expression of genes encoding tight-junction proteins during long-term fermentation of milk. In conclusion, we confirmed that long-term fermentation could be a novel manufacturing process for fermented milk containing <i>L. casei</i> HY2782 and showed the beneficial effects.
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