Document Type : Original Article
Authors
1
Department of Microbiology, Minudasht branch, Islamic Azad University, Minudasht, Iran
2
Department of Microbiology, Azadshahr branch, Islamic Azad University, Azadshahr, Iran
3
Department of Microbiology, Gorgan branch, Islamic Azad University, Gorgan, Iran
4
Department of Biology, Gorgan Branch, Islamic Azad University, Gorgan, Iran
Abstract
Background: Traditional dairy products can be a very suitable reservoir for beneficial microorganisms such as probiotics. This study aims to isolate lactic acid bacteria from yellow curd, a traditional dairy product of Sistan and Baluchestan province located in the southeast of Iran. Methods: The samples were cultured in MRS agar and suspicious colonies, gram positive and catalase negative, using some biochemical tests including fermentation of sugars tests, growth at 10 and 45°C and 6.5% NaCl were identified. Antibacterial activity of culture supernatant of isolates against four gastrointestinal pathogens was performed by disk and well methods. Also, the tolerance of isolates to acidic conditions and bile salts was measured. Results: Two isolates were identified, that after identification procedures, they were identified as Lactobacillus brevis and Lactococcus lactis. The antibacterial activity of two isolates was well observed, especially by the well method. The diameter of inhibition zone of E. coli, S. dysenteriae, S. aureus and B. cereus in contact with L. brevis culture supernatant was 16, 12, 12 and 8 mm respectively. L. brevis showed more antibacterial activity in both disc and well methods compared to Lc. lactis. The results of the tolerance tests of bile salts and acidic pH for LAB isolates obtained indicated that L. brevis was more tolerant than Lc. lactis. Conclusions: In general, yellow curd produced by traditional methods, can be considered beneficial carriers for bacteria with probiotic potential. In between the probiotic potential of L. brevis isolate was evaluated favorably.
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