β-glucosidase from the grape native yeast Debaryomyces vanrijiae:: Purification, characterization, and its effect on monoterpene content of a Muscat grape juice

Six hundred ten yeast colonies isolated from various vineyards in Chile were screened for the presence of a beta-glucosidase activity as well as the resistance to glucose and ethanol inhibition. Among them, Debaryomyces vanrijiae was found to produce high levels of an extracelular beta-glucosidase which was tolerant to glucose (K-i = 439 mM) and ethanol inhibitions. The enzyme (designated DV-BG) was purified to apparent homogeneity,respectively, by gel filtration, ion-exchange, and chromato-focusing techniques. Its molecular weight was 100 000, and its pl 3.0, optimum pH, and temperature activities were 5.0 and 40 degreesC, respectively, and had a V-max of 47.6 mumol min(-1) mg(-1) and a K-m of 1.07 mM. The enzyme was active against different beta-D-glucosides including glucosidic flavor precursors. The disaccharidic flavor precursors were not substrates for the enzyme. When added to a Muscat grape juice, the concentration of several monoterpenes increased as the consequence of its hydrolytic activity.