Introduction. Lactic acid bacteria with known metabolic properties contribute to the sensory characteristics of the products, to their quality and safety. The limited number of highly biotechnologically available strains and the constant risk of bacteriophage attacks justify the continued searching for new strains.Materials and methods. Identification of thermophilic lactic acid bacteria was performant on the basis of phenotypic properties and using molecular methods -RAPD-PCR and FTIR spectroscopy. Antagonistic activity of selected strains was carried out by diffusion method. Starter culture and samples of yoghurt were manufactured according to the traditional technology.Results and discussion. Selected strains of S. thermophilus are characterized by intense acidification of the milk for 3-4 hours, developing a milk acidity between 65-74 °T, forming a homogeneous, compact, dense coagulum, which ensures its firm consistency. The strains S. thermophilus strains CNMN-LB-50 and CNMN-LB-51 are capable of synthesizing exopolysaccharides (EPS).The antagonistic activity against pathogenic microorganisms of strains of is high. The inhibition range varies between 16 and 18 mm from Escherichia coli. and 19-21 mm to Staphylococcus aureus, which inhibits the development of intestinal infections and prevents the development of pathogens in fermented milk samples. The maximum yeld of EPS synthesized at suboptimal temperature of 32 °C is 19.4% higher than at the optimal temperature for this process (40 °C) for S. thermophilus CNMN-LB-50 strain and 23, 8% for S. thermophilus CNMN-LB-51 strain. To stimulate the synthesis of EPS under industrial conditions in the manufacture of fermented milk products without altering the temperature, the nutrient medium should be supplemented with sucrose in an amount of 8%.Conclusions. It is possible obtaining from the microflora of raw milk and dairy products of spontaneous fermentation the autochthonous strains of lactic bacteria with valuable biotechnological properties, intended for use in the composition of starter cultures for the production of fermented milk products.
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