PROTEINASE, PEPTIDASE AND ESTERASE-ACTIVITIES OF CELL-FREE-EXTRACTS FROM WILD STRAINS OF LACTOBACILLUS-DELBRUECKII SUBSP BULGARICUS AND STREPTOCOCCUS-SALIVARIUS SUBSP THERMOPHILUS ISOLATED FROM TRADITIONAL GREEK YOGURT

Proteinase, peptidase and esterase activities were detected in cell-free extracts of four Lactobacillus delbrueckii subsp. bulgaricus and four Streptococcus salivarius subsp. thermophilus strains. Post-electrophoretic detection was based on hydrolysis of L-leucine-β-naphthylamide and α-naphthylacetate. The substrates L-leucine-p-nitroanilide, N-acetyl-L-alanine-p-nitroanilide, 2-nitrophenylbutyrate and 4-nitrophenylbutyrate were used for the spectrophotometric detection of the enzymes. Estimation of total proteolytic activity was based on hydrolysis of bovine whole casein. Interesting differences were observed between the two French strains and those isolated from traditional Greek yogurt. © 1990, Proprietors of Journal of Dairy Research. All rights reserved.