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Exploring the diversity of a collection of native non-Saccharomyces yeasts to develop co-starter cultures for winemaking

Binati, Renato L., Innocente, Giada, Gatto, Veronica, Celebrin, Alessandro, Polo, Maurizio, Felis, Giovanna E., Torriani, Sandra
Food research international 2019 v.122 pp. 432-442
Candida zemplinina, Lachancea thermotolerans, Metschnikowia, Saccharomyces cerevisiae, Starmerella, acidity, enzyme activity, ethanol, fermentation, genotyping, glycerol, grape must, inoculum, internal transcribed spacers, lactic acid, random amplified polymorphic DNA technique, starter cultures, stress tolerance, wine industry, winemaking, wines, yeasts
The inoculation of Saccharomyces cerevisiae starter cultures in grape musts is a common practice in wineries worldwide; however, native non-Saccharomyces yeast species are increasingly investigated as co-starters to augment the complexity and regionality of wine. In this study, an extensive collection of non-Saccharomyces yeasts from high-sugar matrices was created and screened with the aim to discover new strains with potentially positive oenological traits. After mining >400 yeasts from 167 samples collected across multiple Italian regions, the isolates were identified based on RAPD-PCR analysis and ITS sequencing. About one quarter of them, belonging to the genera Starmerella, Lachancea and Metschnikowia, were picked up for an in-depth molecular and physiological characterization, since these yeasts were well strewed and have a good oenological reputation. Following the genotyping, stress tolerance assays, enzymatic activity trials and single inoculum fermentations, a huge diversity was acknowledged within and between the species. Strains of S. bacillaris showed a high tolerance to ethanol and increased glycerol production, L. thermotolerans reduced volatile acidity while increasing total acidity with lactic acid, and Metschnikowia spp. exhibited remarkable aroma-related enzymatic activities, which are all prized features in winemaking. Since most of the characteristics analyzed were species and strain dependent, the obtained results are valuable for the selection of a new generation of co-starters for attempting mixed fermentation strategies aimed to improve the overall quality of regional wine.