Peptidase activities in debittering and nondebittering strains of lactobacilli

Three Lactobacillus casei strains, which were isolated earlier from Cheddar cheese and which exhibited debittering and nondebittering effects during cheese ripening, were analysed for their peptide hydrolase systems. All strains exhibited an active aminopeptidase, a dipeptidase, a tripeptidase, a dipeptidyl aminopeptidase and a carboxypeptidase. The most significant difference between debittering and nondebittering strains was observed at the specific activity level of the aminopeptidase. The stability of the aminopeptidase in cheese was also investigated, and it was seen that this enzyme remained active for at least 2 months before its activity began to decrease.