Antifungal properties of 19 Lactobacillus plantarum strains isolated from Lighvan cheese during different production stages were evaluated against Penicillium expansum (ATCC 36200) and Rhodotorula mucilaginosa (ATCC 2503). To accomplish such comparison, culture-based methods including Lawn on the Spot and Well Diffusion were performed and strains with antifungal property were screened. From a pool of 19 strains, 10 of Lb. plantarum spp. exhibited antifungal activity against Pen. expansum and 11 of them against R. mucilaginosa. Thereafter the effects of pH (ranged from 2 to 7) and temperatures (80 °C for 1 h, 100 °C for 10 and 30 min, and 121 °C for 15 min) were evaluated. All Lb. plantarum spp. maintained their inhibitory effect at pH of 2 and 3, while no inhibition was observed at pH of 7. Inhibitory effect intensity decreased by increasing the temperature/time duration of heating. Lb. plantarum C28 showed the highest thermal resistance and also with inhibitory activity of 160 (AU/ml) possessed the highest anti-fungal activity using titration test. The strains LF51, C24, LF49 and LF51, C24 exhibited anti-mold and anti-yeast activity respectively after a 20-fold concentration of the cell free supernatant against Pen. expansum and R. mucilaginosa. Inhibitory effects of all isolates were lost when subjected to proteinase K which implies their proteinaceous nature.

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