Lactic acid bacteria play a key role in human health. These friendly bacteria as a part of the microflora of the gastrointestinal tract (GIT) have a beneficial influence on microbial balance. The probiotic cultures stimulate the growth of beneficial microorganisms, crowd out potentially harmful bacteria and reinforce the body's natural defense mechanisms. Recent data improve the positive effects of probiotics and stimulate research for discovering of new lactic acid bacteria strains with

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... ic properties. In present work the probiotic potential of 23 strains lactic acid bacteria, isolated from Bulgarian rye sourdoughs from different geographical regions was studied in vitro. Their affiliation to the genus Lactobacillus and Pediococcus was determined by classical phenotyping methods. Screening of the strains at selecting factors high acidity and different concentrations of bile salts was first accomplished. In addition, susceptibility to antibiotics, production of hydrogen peroxide and spectrum of antimicrobial activity were determined. After primary selection, 8 strains were chosen and they were tested in a model system for in vitro simulation of the conditions into the human GIT. As a result, two strains with high probiotic potential were found.