ISOLATION AND IDENTIFICATION OF PROBIOTIC LACTIC ACID BACTERIA AND EXAMINATION OF THEIR TOLERANCE AGAINST STRESS FACTORS

Probiotics are living microorganisms which have beneficial effect on the metabolism of the host organism when they pass into the large intestine. The number of living cells declines dramatically when they are going through the gastro-intestinal system, thus consumption of probiotic products with higher cell concentrations is recommended. Potential probiotic lactic acid bacterial strains were isolated from different yoghurts and food supplements and identified by traditional microbiological and molecular biological methods. According to the results the isolated strains belonged to Lactobacillus acidophilus, L. casei, L. rhamnosus, L. helveticus and L. delbrueckii subsp. bulgaricus. The tolerance of L. acidophilus, L. casei and L. rhamnosus against lactic acid, sodium chloride and sucrose was investigated by determination of the growing ability of the strains in a culture media containing different concentrations of these compounds. Among the tested strains L. rhamnosus had similar growth rate as L. casei in lactic acid and media sucrose containing, while it showed a better tolerance for sodium chloride. L. acidophilus strain proved to be more sensitive for lactic acid and sucrose as the above mentioned strains.