Isolation and Biochemical and Molecular Identification of Lactobacilli from Traditional Dairy in Fars Province and Investigation of Their Probiotic Potential

Lactobacilli are the most well-known strains with probiotic properties that have a great effect on promoting gastrointestinal health. The purpose of this study was to isolate and evaluate the probiotic properties of local Lactobacillus in dairy products in Fars province. Gram-positive and catalase-negative bacilli were isolated and analyzed from dairy samples by chemical methods. To evaluate the probiotic properties of the isolates, their growth rate was measured at different acidic and alkaline pHs, different concentrations of bile salt and NaCl salt. The antimicrobial activity of the isolates on pathogenic bacteria was investigated by agar well diffusion method and also susceptibility testing to common antibiotics was performed by disk diffusion method. Optimal strains were identified molecularly by 16 S rRNA gene sequencing. Out of 36 gram-positive and catalase-negative strains, 10 strains were biochemically similar to Lactobacilli that 5 strains being able to grow at pH 3 to 9 and different concentrations of bile salt and NaCl salt. These bacteria had antimicrobial activity against common pathogens and were resistant to the antibiotics Clindamycin, Ampicillin, Erythromycin, and Tetracycline. Strains M3 and Y4 had better probiotic properties. Molecular evaluation showed that these two strains are 100% and 99.98% similar to Lactobacillus brevis and Lactobacillus casei strains, respectively. As a result, it was found that these two strains of Lactobacillus with approved probiotic properties are available in traditional dairy products in Fars province, which can be used in the dairy food industry to improve the quality of livestock and poultry feed.