Biochemical properties of enterococci relevant to their technological performance

A total of 129 E. faccium, E. faecalis and E. durans strains of food, veterinary and human origin were screened for biochemical properties relevant to their technological performance. Strains exhibited low milk acidifying ability and low extracellular proteolytic activity, with food origin and E. faecalis strains being generally more active. Their peptidase activities were low and mainly specific against glycine-proline- and glutamate-4-nitroanilide, while only food origin and E. durans strains showed broader substrate specificity. In contrast, their lipolytic activities were relatively higher; food and veterinary origin and E. faecalis strains were the most lipolytic. The post-electrophoretic detection of esterase activities showed that the esterolytic system of enterococci was rather complex. All species showed strain-to-strain variation in their ability to metabolise citrate and pyruvate, with E. faecalis strains being generally more active. The main volatile compounds produced in milk were acetaldehyde, ethanol and acetoin; generally, E. faecalis strains produced the highest concentrations. None of the strains decarboxylated histidine, lysine and ornithine, but the majority produced tyramine from tyrosine, independently of origin and species. In respect of most biochemical properties considered in this study, E. faecalis strains were generally more active compared to E. faecium and E. durans. This was also the case for the isolates of food origin compared to those of veterinary and human origin. Results obtained allow the selection of enterococci strains to be used as adjunct starters in food fermentations, However, a final selection should take into account the potential virulence factors of enterococci. (C) 2001 Elsevier Science Ltd. All rights reserved.