IDENTIFICATION AND CHARACTERIZATION OF PROTEOLYTIC ACTIVITY OF ENTEROCOCCUS SPP. ISOLATED FROM MILK AND RONCAL AND IDIAZABAL CHEESE

Roncal and Idiazabal cheeses are manufactured from ewe's milk in the A utonomous Region of Navarre in Spain. Levels of enterococci are high i n these cheeses and in other types of ewe's-milk cheeses. The present study has identified enterococci present in the milk used and in the R oncal and Idiazabal cheeses after 120 days of ripening. A total of 282 strains were isolated and identified, and the cytoplasmic and extrace llular enzymatic activities of some of the strains were assessed. The dominating species were Enterococcus faecalis, which accounted for 85% of the total both in the milk as well as in the two types of cheese, and Enterococcus faecium, Enterococcus durans, and Enterococcus avium which were present in lower proportions. Aminopeptidase and proteinase activity levels in enterococci were low, and considerable variation b etween strains of the same species was recorded, highlighting the need to study individual strains when selecting the most suitable bacteria as a starter culture. Aminopeptidase activity levels for the enteroco cci were appreciably higher at pH 7 than at pH 5.5, hence aminopeptida se activity by enterococci would appear to be less significant in the normal manufacturing conditions of the two cheeses. (C) 1997 Elsevier Science B.V.