HEMOLYTIC-ACTIVITY, PRODUCTION OF THERMONUCLEASE AND BIOGENIC-AMINES BY DAIRY ENTEROCOCCI

Seventy-five strains of enterococci isolated from dairy products and b elonging to Enterococcus faecalis and Enterococcus faecium were screen ed for hemolytic activity and production of deoxyribonuclease (DNase), thermonuclease (TNase) and biogenic amines. Although 4 out of 75 stra ins exhibited beta-hemolysis on blood agar, DNase or TNase-producers w ere not detected. MDA (Modified Decarboxylating Agar) medium supplemen ted with 2% L-tyrosine as precursor allowed a large number of tyrosine -decarboxylating strains to be recognized. After incubation in milk co ntaining free amino acids as precursors (200 ppm), the production of b iogenic amines was quantified by HPLC and confirmed as tyramine, where as histamine was never detected. it is suggested that dairy enterococc i represent a possible group of food grade microorganisms.