Caseinolytic Activity of Micrococci Isolated from Cheddar Cheese

Abstract

Micrococci counts of Cheddar cheese, plated throughout ripening, never ex- ceeded 10 X 103 and, after 3.5 months of ripening, few micrococci (less than 10 X 10") grew on the selective tryp- tone agar medium. Eighteen micrococci were isolated from 5 lots of cheese at various times during ripening. Three of these formed extracellular proteinase which hvdrolyzed preferentially a~-casein. Intracel(ular extracts from all isolates degraded preferentially the r-casein moiety of isoelectric casein. Casein hy- drolyzates did not stimulate acid pro- duction by a Cheddar cheese Lactobacil- lus isolate. r-Casein component of m/cellar or isoelectric casein was degraded rapidly by the intracellular extracts. However, proteinase(s) did not hydrolyze purified r-casein as rapidly. Apparently, frac- tionation and purification modify fi-case- in such that resistance to proteolysis is imparted.