DIVERSITY OF PROTEOLYTIC-ENZYMES AMONG LACTOCOCCI

The diversity of various proteolytic enzymes among industrially used s trains of Lactococcus lactis subsp. lactis and Lactococcus lactis subs p. cremoris was investigated. We have determined the activity of isola ted lactococcal proteinases, in the absence and presence of 1.2 M NaCl , towards two differently charged chromophoric peptides. In this compa rative study proteinase specificities among strains were identified as Pill-type, PI-type or intermediate type. Furthermore, we have determi ned the specific activities of the peptidases aminopeptidase N (PepN), X-prolyl dipeptidyl aminopeptidase (PepXP), aminopeptidase A (PepA) a nd pyrrolidonyl carboxylyl peptidase (PCP) in cell free extracts of la ctococcal strains. Specific peptidase activities were found to vary 10 -fold for PepN and PepXP, 1-fold for PepA and 13-fold for PCP. The rol e of the proteolytic enzymes in cheese ripening, in particular, the de velopment of bitterness, is discussed. The diversity of proteolytic ac tivities may reflect different capacities of starters to produce and d egrade bitter peptides derived from the milk proteins.