Broth culture of the LAB strain was centrifuged (13,000 g, 5 min), washed with sterile phosphate-buffered solution (PBS: 8 g/L NaCl, 0.2 g/L KCl, 1.42 g/L Na2HPO4, and 0.27 g/L KH2PO4) three times and re-suspended in PBS to adjust the density of LAB to 1 × 109 cell/mL.