Evaluation of the Antimicrobial Properties of Potential Probiotic Lactic Acid Bacteria from Raw and Fermented Cow Milk.

Background Lactic acid bacteria (LAB) are members of Lactobacillaceae family, the main feature of which is the ability to form lactic acid as a major fermentation product. Lactic acid bacteria are Gram positive, non-spore formers, non-motile, with frequently in chain and catalase negative. Probiotics can be a great substitute for antibiotics. Objective The aim of this study was to isolate, characterize and evaluate probiotic lactic acid bacteria from fermented and raw cow milk. Method In this study, twenty five samples of fermented and raw cow milk from South and North Gondar areas were analyzed and twenty isolates were found. The bacteria were isolated using selective media MRS agar (de Man, Rogasa, and Sharpe).Based on morphological and different biochemical tests isolates were assumed to be Lactobacillus strains Lactobacillus lactis, Lactobacillus casei, Lactobacillus bulgaricus, Lactobacillus fermenti, Lactobacillus brevis and Lactobacillus buchneri . The probiotic potential of isolates was checked using different conditions which full fill the environment of gastrointestinal tract of human and animal, including growth at different pH, NaCl and temperature. The antimicrobial activity of culture filtrate was done by well diffusion method against selected Gram positive and Gram negative bacteria pathogens. Results The hemolytic activity of isolates was done and all were failed to form any zone around colonies, so that they showed γ-hemolysis. In the test isolates were resistance to antibiotics Vancomycin and Gentamycin and very susceptible for Bacitran, Ampicillin, Tetracycline and penicillin. All isolates were effectively inhibit gram positive bacteria S. aureus with a maximum inhibition zone of 27mm and minimum inhibition zone of 15mm. The minimum inhibition zones were recorded from E.coli having a maximum inhibition zone 13mm and minimum inhibition zone 8mm. P.aurogenes and S.thyphi were also inhibited by all isolates having maximum inhibition zone 17mm and 14mm respectively and minimum inhibition zone 10mm and 8mm respectively. Conclusion The result obtained from this study demonstrates the probiotic potential of isolated strains from raw and fermented cow milk and recommended to use in industrial application.