Molecular identification and osmotolerant profile of wine yeasts that ferment a high sugar grape must

Abstract

The objective of this study was to examine the Saccharomyces and non-Saccharomyces yeast populations involvedin a spontaneous fermentation of a traditional high sugar must (Vino cotto) produced in central Italy. Molecularidentification of a total of 78 isolateswas achieved by a combination of PCR-RFLP of the 5.8S ITS rRNA region andsequencing of the D1/D2 domain of the 26S rRNA gene. In addition, the isolateswere differentiated by RAPD-PCR.Only a restricted number of osmotolerant yeast species, i.e. Candida apicola, Candida zemplinina and Zygosaccharomycesbailii, were found throughout all the fermentation process, while Saccharomyces cerevisiae prevailedafter 15 days of fermentation. A physiological characterization of isolates was performed in relation to theresistance to osmotic stress and ethanol concentration. The osmotolerant features of C. apicola, C. zemplinina andZ. bailii were confirmed, while S. cerevisiae strains showed three patterns of growth in response to differentglucose concentrations (2%, 20%, 40% and 60% w/v). The ability of some C. apicola and C. zemplinina strains togrowat 14% v/v ethanol is noteworthy. The finding that some yeast biotypes with highermultiple stress tolerancecan persist in the entire winemaking process suggests possible future candidates as starter for Vino cottoproduction.[...