To test the antibacterial activity of the LAB strains, the agar diffusion method was used according to the description in Lamari et al. (2014). However, in this test, Polymyxin B (1 mg/mL) and MRS broth were added into one well of each plate as positive and negative controls, respectively. The capacity of inhibition is presented as the ratio of the inhibition zone diameter of the LAB strain to that of Polymyxin B.