Abstract:

Lactobacillus paracasei NCU622 was examined for resistance to acid and bile, adhesion to Caco-2 cells, and
cytotoxicity against Caco-2 cells. Furthermore, the impacts of bacterial concentration, incubation time and growth stage
on the adhesion were also studied. It was found that L. paracasei NCU622 showed a survival rate of 98.21% after 3 h
incubation in MRS broth adjusted to pH 2.5. The survival rates of L. paracasei NCU622 were 95.14% and 85.07% after
4 h incubation in MRS broth supplemented with 0.3 and 0.5 g/100 mL oxgall, respectively. The adhesion ((21.19±0.94)
CFU/Caco-2 cell) of L. paracasei NCU622 was very excellent which was affected by the bacterial concentration, incubation
time and growth stage. Moreover, L. paracasei NCU622 did not cause Caco-2 cells lysis after 24 h co-culture. In summary,
L. paracasei NCU622 tolerated well acid and bile, expressed high adhesion to Caco-2 cells, and did not cause Caco-2 cells lysis.
These results demonstrate that L. paracasei NCU622 presents favorable strain-specific properties for its utilization as probiotics in
microecologics and fermented functional foods, and may have broad prospects for applications in fermented and functional foods.

Key words: L. paracasei NCU622, acid tolerance, bile tolerance, adhesion, cytotoxicity