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In this experimental study, the effect of pH (2, 4, 11), temperature (4, 85, 121 oC) and bile salt (0.3, 0.6, 1%) treatments on inhibitory potential of cell-free supernatant (CFS) obtained from barley sourdough dominant LAB (Pediococcus stilesii, Weissella cibaria, Lactobacillus brevis and Lactobacillus curieae) isolates, against B. subtilis were investigated based on microdilution method in comparison to untreated CFS. The safety of LAB isolates was also assessed by control of changes in serum parameters and liver enzymes in mice fed with them. Results were analyzed by one-way analysis of variance. Based on results, LAB CFS had antagonistic activity against B. subtilis. Inhibitory effects of the CFS under pH and temperature treatments were decreased, but under bile salt treatment was increased. Changes in serum parameters and liver enzymes in mice fed with LAB isolates were also in normal ranges and so on, safety of the LAB isolates was approved. By considering the antagonistic activity of LAB CFS under pH, temperature and salt treatments, against B. subtilis it is possible to use from the CFS as a biopreservative in food processing chain.

In this study, strains of lactic acid bacteria capable of bacteriocin production were isolated from Lighvan cheese samples obtained from East Azerbaijan, Iran. Among 16 isolates initially identified as Lactococcus lactis, four isolates were phenotipically determined as bacteriocinogenic. The isolates showed inhibitory effect on the growth of Gram-positive food borne pathogens including Staphylococcus aureus, Bacillus cereus, Clostridium perfringens and Listeria monocytogenes by the agar spot test. Selected isolates were PCR-positive for nisin-encoding gene. The strains produced antibacterial substances resistant to α-amylase but sensitive to trypsin and proteinase K. Thermo-stability was indicated after treatment at 100 °C for 30 minutes. The antibacterial activity was pH dependent and occurred in pH 3 and 6, but at pH 9 the antibacterial activity was mainly restricted. No loss in antibacterial activity was recorded after treatment with SDS, Tween20, Tween 80, Triton X-100, urea and EDTA. The results suggest the potential application of these isolates as biopreservatives in food products.