PEPTIDASE AND PROTEINASE ACTIVITY OF LACTOCOCCUS-LACTIS, LACTOBACILLUS-CASEI AND LACTOBACILLUS-PLANTARUM

The proteolytic system of several non-commercial strains of lactococci and lactobacilli that were isolated directly from traditional-Spanish , semi-hard, goats' milk cheese was studied. The aminopeptidase, X-pro lyl-dipeptidyl aminopeptidase, dipeptidase and proteinase activity of these new strains was measured for the cytoplasmic, cell-wall/membrane and spontaneously released fractions. The aminopeptidase activity was exclusively intracellular and higher for Lactobacillus casei subsp. c asei than for Lactococcus lactis subsp. lactis. Lactobacillus plantaru m showed higher dipeptidase activity than L. casei. The highest level of proteinase activity was recorded for the cell-wallmembrane fraction of Lactococcus lactis subsp. lactis IFPL 359, and was higher on beta- casein than on alpha(s)-casein for all the strains studied. These resu lts suggest some different contribution of these strains to the proteo lysis of cheese during ripening and they seem to complement each other when used together in the starter culture.