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Hydrolysis of major dairy proteins by lactic acid bacteria from Bulgarian yogurts
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International audience. Twenty-one Lactobacillus strains isolated from three types of Balkan homemade yogurts were grown on sodium caseinate, beta-casein or whey proteins, and the proteolysis was followed by electrophoresis and reversed-phase high-performance liquid chromatography. The best conditions allowing obtaining proteolysis without casein precipitation are 0.8% casein in 50-mM phosphate buffer. The strains tested showed a relatively high proteolytic activity despite the limited conditions for bacterial growth. Within 72 and 96 h of incubation, 80-90% of beta-casein was consumed. They showed also a proteolytic activity toward alpha-lactalbumin (ALA), being able to reduce its concentration between 5 and 55%, depending on the strains used. The capacity of the strains to hydrolyze beta-lactoglobulin was lower as compared with hydrolysis of ALA. Hydrolysis of casein by all strains produced peptides with an antibacterial effect against Escherichia coli. Consequently, to obtain a maximal hydrolysi! s of the dairy proteins seconded by appearance of antimicrobial peptides, a combination of strains with different beneficial properties to be used as starters was proposed.
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