Antibacterial activity of cow milk fermented by kefir grains against a number of pathogenic bacteria
Subject Areas : Industrial Food Microbiology
هادی کوهساری
1
,
Seyede Sorayya Sajjadi
2
,
Araz Soltan Saedifar
3
,
Maryam Sadegh Shesh Poli
4
1 - استادیار گروه میکروبیولوژی، واحد آزادشهر، دانشگاه آزاد اسلامی، آزادشهر، ایران
2 - Graduated student, Department of Microbiology, Minudasht branch, Islamic Azad University, Minudasht, Iran
3 - Graduated student, Department of Microbiology, Minudasht branch, Islamic Azad University, Minudasht, Iran
4 - Graduated Ph.D of Molecular Medicine, Golestan University of Medical Sciences, Gorgan, Iran
Keywords: Kefir, Antibacterial activity, Cow milk, Pathogenic bacteria,
Abstract :
Kefir beverage is one of the oldest fermented milk products, which is a natural probiotic and a complex of microbial symbiotic that is obtained from the fermentation of milk by kefir grains. The study aimed antibacterial activity of kefir samples prepared with cow milk against 10 pathogenic bacteria. Kefir grains were added to cow milk (Full-fat and low-fat) and fermentation was done at 25°C and 37°C. Grains were separated from kefir extract and the antibacterial activity of kefir extract was evaluated against 10 pathogenic bacteria by well method. Kefir samples prepared at 37°C compared to 25°C samples showed more antibacterial activity against S. aureus, P. aeruginosa and native K. pneumoniae isolated. The most antibacterial activity of kefir samples against E. faecalis and S. dysenteriae was related to the samples prepared with low-fat milk at 37°C, respectively, with the average diameter of inhibition zone of 18.5 and 12.5 mm. The samples prepared with full-fat milk in 25°C and 37°C indicated more antibacterial activity with the diameter of inhibition zone of 22 and 19 mm against the standard K. pneumoniae strain, respectively. Significant difference was not observed about milk type and fermentation temperature effect on antibacterial activity against E. coli, both native isolate and standard strain and S. typhimurium (P<0.05). B. cereus showed significant resistance to kefir samples. Kefir prepared with cow milk is recommended due to significant antibacterial activity.
