Preparation of Cell-Free Supernatant (CFS). Each LAB isolate was inoculated in 10 mL of MRS broth and incubated at 30∘C for 48 hrs. After incubation, a cell-free supernatant was obtained by centrifuging the bacterial culture at 6000 ×g for 15 min followed by filtration of the supernatant through 0.20