Isolation and identification of Lactobacillus bacteria with probiotic potential from traditional dairy in Kerman

As lactobacilli possess an antagonistic growth property, therefore they may be used as bioprotective agents for infection control. The aim of this study was to investigate the antagonistic effect of lactobacilli isolated from local dairy.
In this study 26 species of Lactobacilli were isolated from milk, homemade yoghurt and cheese. Each isolated bacteria was tested for its tolerance to acidic environments at pH (2.0, 3.0, and 4.0) and bile salt concentrations (0.3, 0.5 and 1% w/v). Also, isolates were further tested for their antimicrobial activity against common pathogenic bacteria such as Enterococcus feacalis, Listeria monocytogenes, Staphylococcus aureus PTCC 1112, Escherichia coli PTCC 1330 and Bacillus cereus PTCC 1015 by using the agar well method. Then the strains that are not only resistant to acidic conditions and bile salts but also have antimicrobial activity, were identified by 16S rRNA gene sequencing.
In this study, most of isolated Lactobacilli were found to inhibit growth of pathogens (96.15%). 61.5% and 84.62% of isolated lactobacilli tolerated to pH 2 and 0.3% bile salt. Only two strains, 53C and 22CL, were more resistant to pH 2 and high concentration of bile salt. The Phylogenetic analysis based on 16S rRNA sequencing revealed that two strains (53C and 22CL) belong to species of Lactobacillus casei.
According the results the two isolated resistant strains can be employed as probiotic starter in probiotic dairy products preparation.