Browsing by Author "Gunata, Z"

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    Influence of a mixed culture with Debaryomyces vanriji and Saccharomyces cerevisiae on the volatiles of a Muscat wine
    (INST FOOD TECHNOLOGISTS, 2002) Garcia, A; Carcel, C; Dulau, L; Samson, A; Aguera, E; Agosin, E; Gunata, Z
    A non-Saccharomyces yeast strain, Debaryomyces vanriji, isolated from grape berry flora was found to Influence wine volatiles of the cv. Muscat of Frontignan when co-cultured with native or inoculated with a selected strain of Saccharomyces cerevisiae during fermentation. The concentrations of several volatiles were significantly different (p < 0.05) between the control and the 2 wines inoculated with D. vanriji. The latter were richer in fatty acids, esters, and terpenols. The increase in geraniol concentration In D. vanriji wines could be attributed to the hydrolysis of the corresponding glucosidic precursor by D. vanriji β-glucosidase. D. vanriji inoculated musts showed higher levels of β-glucosidase activity through fermentation compared to the control sample.
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    β-glucosidase from the grape native yeast Debaryomyces vanrijiae
    (2003) Belancic, A; Gunata, Z; Vallier, MJ; Agosin, E
    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.