Modern development trends of microbial biotechnologies for food industry envisage formulation of bacterial starter cultures ensuring optimal performance of microbiological processes, upgrading product flavor and technological characteristics, showing beneficial effect on human health. Introduction into starter microflora of bacterial strains possessing unique enzyme complexes open new frontiers in modification of dairy processing technologies and elaboration of derived novel products with improved consumer preference characteristics and valuable biological properties. A vital application aspect of starter bacterial cultures is their ability to hydrolyze milk proteins. The process of cheese ripening and upgrading quality and biological value of foodstuffs is largely determined by proteolytic activity of lactic acid bacterial constituents and satellite microbiota. Caseinolytic activity assays were conducted in 36 strains of lactobacteria, newly isolated from diverse natural sources, to screen most promising variants for further use in dairy industry. The bacteria were cultured on whole milk and on casein-less MRS medium. Proteolytic activity of the cultures was estimated by measuring accumulation in the medium of free amino acids tyrosine and tryptophan using Folin reagent. The result was expressed in μmol tyrosine per 1 ml (of) milk. 60 % of examined strains were distinguished by significant level of caseinolytic protease activity. The values assayed in milk medium exceeded 2,5–6 times those recorded on MRS medium. It was found that proteolytic activity of cultures isolated from milk and curd underwent only minor changes during transfer from milk to MRS medium. Subsequent application of isolates in manufacturing fermented dairy products and cheesemaking urged the researchers to monitor peptide and amino acid contents in the course of bacterial cultivation on milk substrate. Significant distinctions in protein utilization pattern were revealed in tested lactic acid bacteria. The peptide and amino acids ratio tended to rise in some strains throughout weeklong fermentation. 7 strains forming well-shaped clots on milk substrate demonstrated presence of peptides and amino acids tyrosine and tryptophan in trace amounts along the whole cultivation period. 9 strains showed full consumption of peptides and amino acids by the end of fermentation. The studies on viability of bacterial isolates, modes of their growth and acidogenesis on various media, the levels of caseinolytic activity in cultural liquid allowed selecting commercially promising strains.