Three hundred sixty-one yeast strains (80 of which ascribable to Saccharomyces cerevisiae) were isolated from Sicilian musts and wines with the purpose of looking for beta-glucosidase (betaG, EC 3.2.1.21) activity. Of these, the AL 41 strain had highest endogenous PG activity and was identified as belonging to the species S. cerevisiae by biochemical and molecular methods. This enzyme was subsequently characterized. It had optimum effect at pH 3.5-4.0, whilst optimum temperature was 20 C, compatible with typical wine-cellar conditions; it was not inhibited by ethanol, at concentrations of 12-14%, or fructose and glucose. The betaG was also characterised in terms of the kinetic parameters K-m (2.55 mM) and V-max (1.71 U mg(-1) of protein). Finally, it remained stable for at least 35 days in model solutions of must and wine.