Rapid enzymatic method for biotyping and control of lactic acid bacteria used in the production of yogurt and some cheeses.

Determination of enzymatic patterns of 30 strains of Streptococcus thermophilus and 18 strains of Lactobacillus delbrueckii subsp. bulgaricus with a rapid APIZYM method was carried out. Alkaline and acid phosphatase, naphthol-AS-BI-phosphohydrolase, 10 esterases, 20 glycosidases, 61 peptidases and 2 proteases (trypsin and chymotrypsin) were included. The strains investigated were isolated from yogurt and from different starters used for different Italian cheeses. For S. thermophilus, all strains were positive for 3 glycosidases, 4 monopeptidases, 9 dipeptidases, 1 tripeptidase and all were negative for 2 esterases; 9 glycosidases; 8 peptidases and trypsin. For L. delbrueckii subsp. bulgaricus it was observed that all strains were positive for 2 esterases; 2 glycosidases; 11 monopeptidases, 9 dipeptidases, 2 tripeptidases and 1 tetrapeptidase and all were negative for alkaline-phosphatase; 3 esterases, 7 glycosidases, 5 monopeptidases, 2 dipeptidases. The defined enzymatic pattern of starter cultures can be used for predicting their suitability for dairy fermentations and for monitoring their stability as well as for typing.