Surface Proteins and Adhesion Properties of Lacticaseibacillus paracasei K56

In this work, the probiotic properties of Lacticaseibacillus paracasei K56 were examined by measuring its ability to tolerate gastrointestinal fluids and its adhesion characteristics. Additionally, the role of its surface proteins in mediating intestinal cell adhesion was investigated by laser confocal microscopy (LCM) and liquid chromatography-mass spectrometry (LC-MS). After 3 h of incubation in artificial gastric fluid, the survival rate of L. paracasei K56 was (88.78 ± 3.31)%, but increased to (91.57 ± 2.24)% when it was transferred into intestinal fluid and further cultured for 2 h. It possessed strong bacteriostatic activity, antioxidant capacity, and good gastrointestinal tolerance. The surface hydrophobicity of L. paracasei K56 toward xylene was (26.24 ± 0.53)%, and the self-polymerization capacity after 5 h was (28.47 ± 1.19)%. Removal of surface proteins decreased the adhesion of L. paracasei K56 to mucin, collagen, and Caco-2 cells. LC-MS analysis identified LPXTG-motif proteins and moonlighting proteins as some of the surface proteins of L. paracasei K56. It was hypothesized that L. paracasei K56’s surface proteins were crucial to the adhesion process, mediating specific adhesion to intestinal epithelial cells and extracellular matrix. The findings of this study offer a theoretical foundation for future research on the utilization and development of L. paracasei K56 in dietary supplements and dairy manufacturing.