Background. Streptococcus thermophilus is traditionally used in association with Lb. delbrueckii subsp. bulgaricus as a starter culture for the production of yoghurt. Some re- searchers have indicated that 5. thermophilus may provide additional health benefits, for example it may reduce cholesterol levels. The aim of this study was to in vitro evaluate the cholesterol uptake and the viability of S. thermophilus isolates in artificial GIT environments. Material and methods. Twelve isolates of S. thermophilus were cultured in artificial gastric fluid (with pepsin added) and in artificial duodenal fluid (with the enzyme complex added), and in M17 broth containing cholesterol at an initial concentration of 600 pg/mL, as well as in M17 broth without cholesterol. Immediately after the adding of bacteria inoculums and at the end of experiment, the concentration of cholesterol and the number of bacteria were measured. Results. S. thermophilus did not remove statistically significant amounts of cholesterol from artificial gastric fluid. The isolates showed the ability to uptake cholesterol from Ml 7 broth and artificial duodenal fluid, and the degree of cholesterol uptake depended on the isolate. Ali isolates of S. thermophilus remove much more cholesterol from Ml7 broth than from artificial duodenal fluid. Ali S. thermophilus isolates had worse survival in artificial gastric or duodenal fluids than in Ml7 broth. Conclusions. The ability of S. thermophilus cells to survive in artificial gastric fluid and artificial duodenal fluid varied according to the isolates.
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