Safety Evaluation of Bacillus Isolates From Fermented Tarhana With Probiotic Potential

Tarhana is a Turkish fermented food that has been widely consumed by Turkish people for hundreds of years. The main fermentation microorganisms are lactic acid bacteria; however, in this study, we aimed to isolate Bacillus strains from tarhana samples and to investigate some probiotic properties after identification. Various types of tarhana samples were collected, and after a preliminary screening test, 53 isolates were selected. The isolates were Gram-positive, endospore-forming, catalase-positive, and motile. Biochemical pathogenicity tests, including lecithinase, DNase, and hemolytic activities, were performed, and all isolates were lecithinase-negative and DNase-negative. Hemolytic tests indicated that eight isolates were gamma-hemolytic and the rest were alpha-hemolytic. Ten virulence genes were investigated in all isolates, and none of them harbored any of these genes. The isolates exhibited strong tolerance to bile salts (78.3%-97.3%) and simulated gastric conditions (81.3%-99.5%). The hydrophobicity potential of the isolates was quite variable, ranging from 14.6% to 76.2%. Aggregation after 24 h ranged from 50.4% to 79.2%. Twenty of the isolates were strong biofilm formers and were susceptible to the antibiotics specific to Bacillus (according to EUCAST). This study revealed the potential of Turkish tarhana as a source of probiotic Bacillus strains.