**3.9 Isolation of probiotics from milk and fermented derivatives**

Mishra and Sharma [115] isolated probiotics from milk and its fermented derivatives such as buttermilk, curd, and cheese. Following direct plating on MRS agar, the colonies were serially diluted in saline water (0.89% NaCl) up to 10-4 before being distributed over MRS agar plates and cultured for 48 h. Purified isolate colonies were streaked on agar plates and morphological features of colonies were used to identify them. Gram staining, catalase test, and carbohydrate fermentation test were used for physiological characterization, and the results revealed five types of isolates, with bacteria isolated from curd and buttermilk samples being gram positive, catalase negative, and capable of fermenting glucose and mannitol without manufacturing gas. The isolates from the cheese and milk samples were determined to be gram negative, thus they were not included in the study. The isolates from the curd sample were further examined for antibacterial activity and antibiotic susceptibility, with positive findings indicating that they belonged to the *Lactobacillus casei* genus.

#### *Probiotics in Processed Dairy Products and Their Role in Gut Microbiota Health DOI: http://dx.doi.org/10.5772/intechopen.104482*

Lactobacilli isolated from traditional milk products of 17 sample samples known in Azerbaijan as tvorog curd cheese. 17 samples have been taken of tvorog, followed by 1 g suspension of each sample in solution of saline. The MRS broth was then added 500 μl of suspension and then it was incubated for the period of 48 h at 37°C. In the concentration of 10.0 ml PBS buffer (pH = 3), 1.0 ml of each cultivation of the enriched culture was incubated for 3 h to detect lactobacilli resistance to severe stomach conditions. The 10 ml of broth was added and incubating at 37°C for the period of 4 h resuscitated pH-resistant bacteria after centrifugation. Another test was performed to determine the bile salt resistance for bacteria. The bacteria that were acid resistant were injected in MRS broth and incubated for 4 h at 37°C. The dilutions were placed on MRS agar plates and incubated for the period of 24–48 h at 37°C. In 10 ml MRS broth, different colonies were selected and cultivated. The isolates were first assessed using gram staining and the morphology of cell. After that, the isolates were stored at −70°C in MRS broth with 10% skim milk and 25% glycerol. All these species have antibacterial properties against the indicator bacterium. Isolation of antibacterial samples by tvorog curd cheese, to determine acid and bile resistant lactobacilli strains, that was identified by 16 s rDNA as *L. plantarum, L. casei, and L. rhomnos*.

Tavakoli [116] gathered five specimens of Koozeh from remote area of Mazandaran province. The sample (30 g) has been homogenized and then incubated for the period of 24 h at 37°C and inoculated in 300 ml of MRS Broth. In the following stage, the pellet was resuspended to be 10 ml phosphate-buffered (PBS) in a 2.5 pH-adjusted phosphate-buffered Saline (PPS), then placed on an MRS agar medium. The plate was incubated in anaerobic circumstances at 37°C for 24–48 h. Colonies of all morphologies were gathered and purified by culture on the same medium. Gram positive, catalase negative isolates were regarded as a presumptive LAB following gramme staining and catalase reactions, which was kept at −80°C in 15% glycerol. The different isolates were examined based on colony morphology (form, superficie and color), cell morphology (form and size), and the biochemical properties of phenotypes and lactobacillus. They were tested. Jayne Williams in 1977 described or explained that the genus Lactobacillus that depends on the morphological state, and biochemical features, has been deemed to include eight bacterial isolates. For the sequencing, the typical 16S rDNA amplicons were picked for each of the several profiles. The homology of the sequence sequences was more than 95% for four distinct Lactic acid bacteria species [117] in terms of molecular identity comparisons. There, *L. plantarum, L. casei, L. pentosus, and L. fermentum* were as follows.
