CELL-WALL ASSOCIATED PEPTIDE-HYDROLASE AND ESTERASE-ACTIVITIES IN SEVERAL CHEESE-RELATED BACTERIA

Cell-wall associated proteinases, peptidases and esterases of Lactobacillus helveticus, Pediococcus sp., Leuconostoc mesenteroides ssp. mesenteroides, Brevibacterium linens, Propionibacterium acidipropionici and Bifidobacterium infantis were assayed. Proteolytic activity was measured using C14-labelled casein. Aminopeptidase, dipeptidase and esterase activities were measured using chromogenic substrates. All the cheese related bacteria tested exhibited cell-wall proteinase activities with highest being detected in Leuconostoc mesenteroides ssp. mesenteroides, Pediococcus sp. and Brevibacterium linens. Lactobacillus helveticus and Brevibacterium linens exhibited greater cell-wall esterase and aminopeptidase activities, but little of the total activities of these enzymes were associated with the cell envelope. Greater properties of total cellular dipeptidase activities were associated with the cell envelope, with Lactobacillus helveticus and Brevibacterium linens exhibiting highest specific activities. The optimum pH of the crude cell-wall proteinase of different strains ranged from pH 5.5 to 8.0 while the optimum temperature ranged from 20 to 40-degrees-C. The impact of proteinase inhibitors tested differed between species.