Proteinase, peptidase and esterase activities of cell-free extracts from wild strains ofLactobacillus delbrueckiisubsp.bulgaricusandStreptococcus salivariussubsp.thermophilusisolated from traditional Greek yogurt

Summary Proteinase, peptidase and esterase activities were detected in cell-free extracts of fourLactobacillus delbrueckiisubsp.bulgaricusand fourStreptococcus salivariussubsp.thermophilusstrains. Post-electrophoretic detection was based on hydrolysis of L-leucine-βnaphthylamide 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.