The aim of this study was to investigate the anti-yeast activity of Lactobacillus strains isolated from two Iranian traditional cheeses, namely Lighvan and Motal, against food spoilage yeast indicators namely: Rhodotorula mucilaginosa (PTCC 5257), Saccharomyces cerevisiae (PTCC 5269) and kluyveromyces lactis (PTCC 5185). Since these yeasts produce gas and cause spoilage in yoghurt drink (Doogh), 20 strains of Lactobacillus strains which were isolated previously from Motal cheese (16 strains) and Lighvan cheese (4 strains) were evaluated with regard to their anti-yeast activity. The anti-yeast activity was studied by Agar Spot and well diffusion assay. The effect of Low Temperature Long Time (LTLT) treatment (30 min at 63 ° C) on stability of inhibitory compounds in cell free extract was also investigated. Results confirmed that lactobacillus strains and their produced metabolites exhibited inhibition on the growth of food spoilage yeasts as clear zone of inhibition. In Agar Spot method, the highest clear zone against Rhodotorula mucilaginosa, Saccharomyces cerevisiae and kluyveromyces lactis were related to M2 (Lactobacillus brevis) with 7.5 mm diameter, M4 (Lactobacillus brevis) with 6.5 mm diameter and LF55 (Lactobacillus plantarum) with a 6.5 mm diameter, respectively. In well diffusion assay, the widest diameter against Rhodotorula mucilaginosa, Saccharomyces cerevisiae and kluyveromyces lactis are related to M4, 7.5 mm (Lactobacillus brevis); M4, 9.5 mm, and M4, 7 mm, respectively. When cell free extract (CFE) of isolates were subjected to LTLT treatment, the highest clear zone against Rhodotorula mucilaginosa, Saccharomyces cerevisiae and kluyveromyces lactis were observed in strain M4 equal to 7 mm; 6.5 mm; and 5 mm. In conclusion, strain M4 showed the highest anti- yeast capability against all 3 indicators. Subjected CFE to LTLT treatment proved that strain M4, Lb. brevis possesses the highest thermal stability.

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