Isolation of Lactobacillus plantarum Strains With Robust Antagonistic Activity, Qualified Probiotic Properties, and Without Antibiotic-resistance From Traditional Sourdough

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Background: The main purpose of the present study was to identify the qualified probiotic strains of traditional sourdough and to find stable Lactobacillus strains with enhanced antibacterial/antagonistic activity and without antibiotic resistance. Methods: Sixteen strains were isolated from traditional sourdough and their susceptibility was evaluated toward a number of different antibiotics. In addition, the isolated strains were assessed with respect to their probiotic properties, antagonistic activity, and resistance to low pH, bile salt, different NaCl concentrations, and low storage temperatures. Results: Based on the results, although none of the strains had considerable antibiotic resistance, they showed significant antagonistic activity against 6 different pathogens. Among the isolates, H3a and K3b were the most resistant to low pH and bile salt (0.3%) and demonstrated most hydrophobicity, auto-aggregation, and coaggregation characteristics. It was also observed that the strains could produce strong biofilm and were viable at 1%-10% NaCl concentrations, as well as at 4° C and -20° C. Finally, the sequencing results revealed that these 2 strains had the highest homology to Lactobacillus plantarum based on the 16S rRNA gene. Conclusions: The present data confirmed the safety of Lactobacillus content of the traditional sourdough and the unique probiotic properties of these strains.