Effect of the JLM Strain Against Strains in Ripened Cheese.

This study evaluated the antagonistic effect of the JLM strain isolated from , against RB51, S19, and 2308 strains, during the manufacture of soft-ripened cheese. First, the tolerance of JLM was tested with pH values and bile salt concentrations for 3 h to simulate digestive tract conditions. The antagonistic effect against strains was evaluated through double-layer diffusion and agar well diffusion assays. In addition, the stability of the cell-free supernatant (CFS) was tested with the agar well diffusion method under different conditions of temperature, pH, and treatment with digestive enzymes. Finally, the antagonistic effect against strains was observed during the manufacture of ripened cheese for 31 days at 4°C and 25°C using the JLM strain as starter culture. The results showed that the JLM strain remains viable after exposure to different pH values (from 3.00 to 7.00) and concentrations of bile salts (from 0.5% to 7%). Moreover, the results demonstrate that the growth of the three strains was inhibited in both antagonism tests and that CFS maintained 86% activity after heat treatment at 100°C, 121°C, or enzymatic digestion (proteinase K, trypsin, chymotrypsin), but it was inactivated at pH levels above 6. Finally, JLM completely inhibited the growth of in ripened cheese at 25°C from day 17 and showed greater inhibition on the RB51 strain in the ripened cheese at 4°C, showing statistical differences for the S19 and 2308 strains. The current research concluded that the JLM strain has an antagonistic effect on , enhancing the potential of its use in the future as a probiotic.