Biochemical properties of Streptococcus macedonicus strains isolated from Greek Kasseri cheese.

A total of 32 Streptococcus macedonicus strains, isolated from Greek Kasseri cheese, were screened for biochemical properties of technological importance in milk fermentation processing, such as acid production, proteolytic and lipolytic activity, citrate metabolism, exopolysaccharide production, antimicrobial activity and biogenic amines production. All strains were found to be moderate acidifiers in milk. Only four strains could hydrolyse milk casein, while 11 strains showed lipolytic activity against tributyrin. Using amino acid derivatives of 4-nitroaniline as substrates, the highest peptidase activities were determined against phenylalanine- and glycine-proline-4-nitroanilide. Using fatty acid derivatives of 4-nitrophenol, it was shown that all strains exhibited esterase activities up to caprylate, with highest values against butyrate and caproate. Only one showed activity up to palmitate; this was also the most active strain against tributyrin. Five of the 32 strains could metabolize citrate but none of them produced exopolysaccharides. Nine strains displayed antimicrobial activity towards Clostridium tyrobutyricum, while no antimicrobial activity was detected against Listeria innocua and Propionibacterium freudenreichii subsp. shermanii. Finally, none was able to decarboxylize ornithine, histidine or lysine, and only four strains produced tyramine from tyrosine.