EXPLORING BIODIVERSITY POTENTIAL OF WINE ASSOCIATED YEASTSSofia Dashko
, 2015, doktorska disertacija
Opis: Human exploitation of yeast fermentation dates back to the Neolithic. S. cerevisiae has been the most important yeast used for numerous fermentations of biotechnological interest, including grape fermentation for wine production. Despite its abundant use, the molecular mechanisms controlling alcoholic fermentation are rather unclear and the choice of S. cerevisiae as an inoculum is often the consequence of a mere habit, rather than the result of rational analyses.
In this work we focused on the role of different yeasts in the winemaking process. I was interested in understanding how the specific strain used for inoculum could influence the wine aroma formation. Furthermore, I wished to investigate the yeast genetics and ecology by characterizing their population and strain diversity in one of the wine regions of Slovenia.
To evaluate the effect of the yeast species on the fermentation outcome, we performed successive fermentations with five different species in combination with the industrial strain S. cerevisiae Lalvin T73. The experiment showed that at least two more yeast species, Kazachstania gamospora and Zygosaccharomyces kombuchaensis have good potential to be applied in the winemaking. , The main conclusions of this study are the possibility of: i) expanding the palette of alternative starters to widen the aromatic components ii) co–fermenting using two different yeast species. Mixed yeast culture fermentations are present in the natural context, but this practice has been neglected in biotechnological processes.
Positive results of wine fermentations with non – conventional yeast urged us to explore the diversity of Slovenian wine region natural isolates. The resulting yeast collection counts more than 1200 strains for which phenotype and genotype have been defined. Numerous isolates, including non – Saccharomyces species, showed promising oenological and biotechnological traits because of their capacity of rapid utilization of various carbon sources, growth at low pH and at presence of copper sulfite and potassium metabisulfite. Sampling also revealed sharp discrimination between the ecological niches of S. cerevisiae and S. paradoxus, which is a striking feature of European vineyards. While S. cerevisiae habitats are strongly associated with human activity, S. paradoxus was mainly isolated from the forest sources. Profound analysis of the collected data could give some explanations to the driving forces of S. cerevisiae domestication and S. paradoxus geographic isolation population structure.
Najdeno v: ključnih besedah
Ključne besede: Yeasts, biodiversity, molecular biology, alcoholic fermentation
Objavljeno: 02.11.2015; Ogledov: 1850; Prenosov: 17
Polno besedilo (41,27 MB)
Isolation and selection wild yeasts for winemakingNatalia Mikhaylina
, 2017, diplomsko delo
Opis: The aim of this study was to explore the diversity of fermentative yeast species in a non-vineyard and vineyard environment, and exploit their oenological potential. For this purpose we collected plant and soil material in the vineyard (located in Črniče in Vipava Valley) planted with Vitis vinifera L. and in the forest (forest in Vipava Old Castle), and by using a selective medium with high ethanol and sugar content we managed to obtain 35 isolates. By sequencing the D1/D2 domain of the 26S rDNA we identified nine different yeast species. The oenological potential of identified yeasts was further investigated by employing a series of tests, such as growth at low pH values, tolerance to ethanol and sulfur, and H2S production ability. Based on the results of these tests we selected four different yeast species for the microvinification of Vitis vinifera L. cv. ‘Pinot Noir’ grape juice. A commercial strain Saccharomyces cerevisiae Lalvin D47 was also included as a control in the fermentation experiment. Fermentation monitoring was done by measuring daily weight loss and microbiological analysis in the middle of fermentation. For the final wines, sugars were determined and sensorial evaluation performed. Among four tested yeasts, S. paradoxus IVV 32 and Torulaspora delbrueckii IVV 36 appeared to be the most promising for winemaking, but further studies should be carried out.
Najdeno v: ključnih besedah
Ključne besede: wine, Vitis vinifera L. cv. ‘Pinot Noir’, biodiversity, yeasts, fermentation
Objavljeno: 10.07.2017; Ogledov: 273; Prenosov: 34
Polno besedilo (2,57 MB)