Screening of β-Glucosidase and β-Xylosidase Activities in Four Non-Saccharomyces Yeast Isolates

The finding of new isolates of non-Saccharomyces yeasts, showing beneficial enzymes (such as -glucosidase and -xylosidase), can contribute to the production of quality wines. In a selection and characterization program, we have studied 114 isolates of non-Saccharomyces yeasts. Four isolates were selected because of their both high -glucosidase and -xylosidase activities. The ribosomal D1/D2 regions were sequenced to identify them as Pichia membranifaciens Pm7, Hanseniaspora vineae Hv3, H. uvarum Hu8, and Wickerhamomyces anomalus Wa1. The induction process was optimized to be carried on YNB-medium supplemented with 4% xylan, inoculated with 106cfu/mL and incubated 48h at 28 degrees C without agitation. Most of the strains had a pH optimum of 5.0 to 6.0 for both the -glucosidase and -xylosidase activities. The effect of sugars was different for each isolate and activity. Each isolate showed a characteristic set of inhibition, enhancement or null effect for -glucosidase and -xylosidase. The volatile compounds liberated from wine incubated with each of the 4 yeasts were also studied, showing an overall terpene increase (1.1 to 1.3-folds) when wines were treated with non-Saccharomyces isolates. In detail, terpineol, 4-vinyl-phenol and 2-methoxy-4-vinylphenol increased after the addition of Hanseniaspora isolates. Wines treated with Hanseniaspora, Wickerhamomyces, or Pichia produced more 2-phenyl ethanol than those inoculated with other yeasts. Practical Application Wines produced with a combination of Saccharomyces cerevisiae and non-Saccharomyces strains could have a better quality than others. Non-Saccharomyces yeasts contribute to aroma enhancement of Muscat wines.