Enzymatic activities of lactic acid bacteria isolated from Cornetto di Matera sourdoughs

Forty-one strains of lactic acid bacteria (LAB) isolated from Cornetto di Matera sourdoughs were screened for their enzymatic activities, to elucidate their possible roles during the fermentation process. Urease, peptidase, phytase, phosphatase and beta-glucosidase activities were measured spectrophotometrically using synthetic substrates. Proteolytic activities were examined in model doughs, using neutral and acidified sterile doughs as controls. All strains had low urease, glutamyl aminopeptidase and iminopeptidase activities, whereas differences within species were observed for the other enzymatic activities. Leuconostoc mesenteroides and Lactobacillus curvatus strains generally showed high aminopeptidase, X-prolyl dipeptidyl aminopeptidase, beta-glucosidase and phytase activities, while the enzymatic activities of Lactobacillus plantarum, Lactobacillus pentosus and Weissella cibaria varied between strains. In order to classify the strains on the basis of similar enzymatic profiles, a hierarchical cluster analysis was carried out. Several strains of L. plantarum, L. curvatus and Leuc. mesenteroides showed an interesting combination of proteolytic, peptidase, beta-glucosidase and phytase activities, suggesting their possible usefulness as a mixed starter culture in bread-making processes.