Enterococci are widespread lactic micro-organisms, in consequence of their resistance and adaptability to different substrates and growth conditions. They can occur also in various foods and particularly in several cheeses, especially of traditonal type, as autochthonous microfloras. In such products their presence is often related to the typical organoleptic characteristics, because of their metabolic properties. Particularly, their proteolytic, lipolytic and esterasic activities can play an important role in flavour and texture formation. In this study 41 enterococcal strains (28 Enterococcus faecalis and 13 Enterococcus faecium) isolated in a previous research from traditional ewe’s raw milk cheeses were analysed for their esterasic activity by a spectrophotometric technique. The detection of esterasic activity of the strains was executed on cell-free extracts of the strains, utilizing the substrate 4-nitrophenyl-butyrate. The esterase activity was finally determined spectrophotometrically at 410 nm. Moreover the protein concentration of the cell-free extracts was determined by a commercial kit, using bovine serum albumin as a standard. On the basis of our results, E. faecium strains generally resulted more esterolytic than E. faecalis strains. Finally, in this study the most interesting strains with regard to their esterolytic capability were determined, in order to select and utilize them as adjunct components in autochthonous starters.
Attività esterasica di enterococchi isolati da formaggi pecorini tradizionali
PEDONESE, FRANCESCA;INNOCENTI, ELENA;NUVOLONI, ROBERTA;D'ASCENZI, CARLO;CERRI, DOMENICO
2005-01-01
Abstract
Enterococci are widespread lactic micro-organisms, in consequence of their resistance and adaptability to different substrates and growth conditions. They can occur also in various foods and particularly in several cheeses, especially of traditonal type, as autochthonous microfloras. In such products their presence is often related to the typical organoleptic characteristics, because of their metabolic properties. Particularly, their proteolytic, lipolytic and esterasic activities can play an important role in flavour and texture formation. In this study 41 enterococcal strains (28 Enterococcus faecalis and 13 Enterococcus faecium) isolated in a previous research from traditional ewe’s raw milk cheeses were analysed for their esterasic activity by a spectrophotometric technique. The detection of esterasic activity of the strains was executed on cell-free extracts of the strains, utilizing the substrate 4-nitrophenyl-butyrate. The esterase activity was finally determined spectrophotometrically at 410 nm. Moreover the protein concentration of the cell-free extracts was determined by a commercial kit, using bovine serum albumin as a standard. On the basis of our results, E. faecium strains generally resulted more esterolytic than E. faecalis strains. Finally, in this study the most interesting strains with regard to their esterolytic capability were determined, in order to select and utilize them as adjunct components in autochthonous starters.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
