Evaluation of the Inhibitory Effect of Enterococcus durans Strains Isolated from Kefir Grains Against Five Foodborne Pathogenic Bacteria

Subject Areas : Food and Agricultural Spoilage

Matin Shafiee ^{1 *} , Yasamin Shafiee ² , Shahla Soltani-Nezhad ³

1 - Health and Wellness Center, Kerman Province Education, Kerman, Iran
2 - Department of Biology and Vector Control, University of Medical Sciences, Kerman, Iran
3 - Department of Microbiology, Ji.C., Islamic Azad University, Jiroft, Iran

Received: 2025-08-08 Accepted : 2025-09-03 Published : 2025-08-03

Keywords: Kefir, probiotic, antibacterial activity, Enterococcus durans, foodborne pathogens,

Abstract :

Kefir is a fermented probiotic beverage with strong antimicrobial properties, derived from kefir grains. This study aimed to isolate and identify bacterial strains present in kefir and evaluate their antibacterial activity against five major foodborne pathogens, including Bacillus cereus, Staphylococcus aureus, Listeria monocytogenes, Escherichia coli, and Salmonella enterica. After culturing the samples on MRS agar and purification, 34 Gram-positive isolates were obtained. Among them, four superior strains with the highest antagonistic activity were selected and subjected to molecular identification. 16S rRNA gene sequencing results revealed that these strains belong to the species Enterococcus durans and were registered in the Gene Bank under accession numbers MT032372 , MT032373, MT032374 MT032375. These strains lacked proteolytic activity but exhibited amylolytic activity and the ability to produce strong antibacterial metabolites. Increasing the fermentation time from 24 to 72 hours led to a significant increase in the diameter of the growth inhibition zones (ranging from 10 to 23 mm). The findings indicate that the Enterococcus durans strains isolated from kefir have high potential for use as biocontrol agents in the food industry and for the production of probiotic products.

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