Determination of antimicrobial effects of lactic acid bacteria isolated from commercial yoghurt specimems

The antimicrobial effects of lactic acid bacteria attract many scientists. Lactic acid bacteria; bacteriocin, hydrogen peroxide, organic acid, reuterine, carbon dioxide, alcohol etc. they form products. These products are effective against some bacteria and fungi. In certain proportions, these microorganisms are known to change the living standards and even end their lives. Products derived from lactic acid bacteria also serve as bioprotectants. One of them is bacteriocin and there are many studies performed on behalf of it. Among the antimicrobial proteins produced by lactic acid bacteria, the most well-known and characterized bacteriocin nisin (E234) is produced by Lactococcus lactis and is the only licensed bacteriocin to be used as a bio-preservative in food, and has a inhibitory effect on Clostridium sporogenes. In this study, a commercially available yogurt sample, a kefir sample, a probiotic bacterial source and the growth fluids of Saccharomyces boulardii were analyzed for their antimicrobial properties. At the end of the study, lactic acid bacteria in yogurt and kefir and probiotic bacteria were determined to have different levels of antimicrobial effect on S. aureus, P. aeruginosa and C. kruseii. Zone diameters of 38.0 and 37.0 mm were obtained on S. aureus. The zone values of 20.0, 22.6 and 31.5 mm were determined on C. kruseii. The diameter of the zone obtained for P. aeruginosa is 18.3 mm. In our study, it has been concluded that the sources containing lactic acid bacteria are important foods for human life thanks to their antimicrobial properties.