Summary -A total of 16 mesophilic homofermentative lactobacilli were isolated from Xynotyri, a traditional Greek cheese. Identification of strains was performed by phenotypic methods and by SDS-polyacrylamide gel electrophoresis of whole-cell proteins; strains were found to belong to the Lactobacillus plantarum species. Peptidase and esterase activities were detected spectrophotometrically and electrophoretically in the cell-free extracts of the strains, using synthetic substrates. The proteolytic activity of whole cells in milk, as weil as the proteolytic activity of cell-free extracts on whole bovine casein were examined. Slqnitlcant differences within the species were observed, allowing the selection of technologically interesting strains.

Isolates of lactobacilli from infant faeces phenotypically characterized as Lactobacillus paracasei subsp. paracasei (six strains), Lact. rhamnosus (six strains), Lact. gasseri (three strains), Lact. acidophilus (one strain) and Lact. fermentum/reuteri (three strains) according to recent classification systems were subjected to SDS-PAGE of whole cell proteins and rRNAtargeted oligonucleotide probe hybridization, in order to confirm the phenotypic characterization and elucidate the exact taxonomic position of the three strains that had properties between fermentum and reuteri. Results suggested a good agreement between the phenotypic characterization, SDS-PAGE and rRNA-targeted oligonucleotide probe hybridization for strains of all species except for the Lact. fermentum/reuteri strains. Results obtained by rRNA probes suggested a possible phylogenetic relatedness of the strains to Lact. reuteri. Isolates from infant faeces with interesting probiotic properties could be used as components of fermented milk products.