Isolation of a potentially probiotic Lactobacillus plantarum from Siahmezgi cheese and its characterization as a potentially probiotic

Introduction: Probiotics are nonpathogen living microorganisms which express beneficial effects on host, when are administered in adequate amounts. Traditional dairy products are regarded as good sources of probiotics. Present study aims to isolate Lactic Acid Bacteria (LAB) from Siahmezgi cheese, a traditional cheese produced in the north of Iran, and to evaluate their probiotic potential for the first time. Materials and methods: LAB was isolated by culturing cheese samples on MRS agar. The isolates were screened for their probiotic potential using in-vitro tests, including tolerance to acid and bile, survival in simulated gastrointestinal tract conditions, βgalactosidase and hemolytic activity as well as antibiotic susceptibility. In addition, antibacterial activity of the isolated strains against E. coli O157 and Salmonella enterica serovar typhimurium ATCC 14028 was determined. Results: One strain, labeled as Lb3 showed the highest tolerance to low pH, bile and simulated gastrointestinal tract conditions. This strain exhibited resistance to Streptomycin, Vancomycin and Polymixin B as well as effective antibacterial activity against two Gram negative pathogens, lacking hemolytic activity as well as high βgalactosidase activity. Finally, the strain Lb3 was identified as Lactobacillus plantarum CJLP55 using biochemical characterization and 16S rRNA sequencing assay. Discussion and conclusion: In the present work, a potentially probiotic Lactobacillus plantarum CJLP55 was isolated from traditionally produced Siahmezgi cheese. The bacterium displayed good probiotic properties and could be used in dairy industry.