Aspetti microbioligici legati alle produzioni enologiche dei territori delle DOC di Conegliano

With the aim of isolating autochthonous yeasts, 411 samples of grape, coming from the Prosecco DOC area, were picked up during 2004-2005 vintage and small scale fermentations were performed. All the isolates were the subjected to a ad-hoc developed genetic analysis, based on multiplex PCR, to identify yeasts belonging to the Saccharomyces sensu stricto group, that is known to include all species with relevant enological properties. A total of 659 isolates were therefore rapidly screened and 308, coming from 31 fermented samples out of 354, were identified as Saccharomyces sensu stricto. DNA from these isolates was further analysed to attain strain-specific characterization and mitochondrial DNA restriction analysis was used to highlight the genetic polymorphism of the isolates. Computer-assisted analysis on similarities of electrophoretic profiles allowed the grouping of the isolates into 38 different clusters. After phenotypic characterization of the 308 isolates, Saccharomyces cerevisiae strains showing interesting enological properties were chosen. In this study, the 66 selected strains were subjected to analyses concerning ethanol resistance, sulphite tolerance and glycosidase activity. Resistance to ethanol was investigated using a plate test, sulphite tolerance was studied by growing cultures into a synthetic grape must mimicking enological conditions and β-glucosidase activity was detected with a fluorimetric method. The fermentation attitude of the best performing strain was tested during pilot-scale vinifications.