THE COMBINED USE OF WHOLE-CELL PROTEIN EXTRACTS FOR THE IDENTIFICATION (SDS-PAGE) AND ENZYME-ACTIVITY SCREENING OF LACTIC-ACID BACTERIA ISOLATED FROM TRADITIONAL GREEK DAIRY-PRODUCTS

A total of 148 strains of lactic acid bacteria from the ACA-DC Collection were examined in this study. They were all isolated from traditional Greek dairy products such as yoghurt and cheese and were assigned to the genera Enterococcus, Lactobacillus, Lactococcus, Leuconostoc and Streptococcus. By use of traditional phenotypic methods 65 strains were identified to the species level; the remaining 83 strains were partially characterised (genus level). The SDS-PAGE technique of whole-cell proteins was evaluated as an advanced tool for the identification of lactic acid bacteria. Therefore protein fingerprints were registered for all strains and compared to a large number of lactic acid bacteria reference strains stored in database format. In most cases the SDS-PAGE analysis confirmed the phenotypic identification results. With only a few exceptions, all partially characterised strains were identified to (sub)species level. In order to quickly reveal characteristics which could be important for their use as starter cultures in dairy fermentations, it is shown that the bacterial cell-free protein extracts could simultaneously be screened for peptidase and esterase activities using synthetic substrates. Obvious differences among the strains, the groups of strains as well as on the genus level were observed