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1.
EXPLORING BIODIVERSITY POTENTIAL OF WINE ASSOCIATED YEASTS
Sofia Dashko, 2015, doctoral dissertation

Abstract: 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.
Found in: osebi
Keywords: Yeasts, biodiversity, molecular biology, alcoholic fermentation
Published: 02.11.2015; Views: 4406; Downloads: 85
.pdf Fulltext (41,27 MB)

2.
Changes in the relative abundance of two Saccharomyces species from oak forests to wine fermentations
Jure Piškur, Justin C. Fay, Lorena Butinar, Sofia Dashko, Helena Volk, Ping Liu, 2016, original scientific article

Abstract: Saccharomyces cerevisiae and its sibling species S. paradoxus are known to inhabit temperate arboreal habitats across the globe. Despite their sympatric distribution in the wild, S. cerevisiae is predominantly associated with human fermentations. The apparent ecological differentiation of these species is particularly striking in Europe where S. paradoxus is abundant in forests and S. cerevisiae is abundant in vineyards. However, ecological differences may be confounded with geographic differences in species abundance. To compare the distribution and abundance of these two species we isolated Saccharomyces strains from over 1,200 samples taken from vineyard and forest habitats in Slovenia. We isolated numerous strains of S. cerevisiae and S. paradoxus as well as small number of S. kudriavzevii strains from both vineyard and forest environments. We find S. cerevisiae less abundant than S. paradoxus on oak trees both within and outside the vineyard, but more abundant on grapevines and associated substrates. Analysis of the uncultured microbiome shows that both S. cerevisiae and S. paradoxus are rare species in soil and bark samples, but can be much more common in grape must. In contrast to S. paradoxus, European strains of S. cerevisiae have acquired multiple traits thought to be important for life in the vineyard and dominance of wine fermentations. We conclude that S. cerevisiae and S. paradoxus currently share both vineyard and non-vineyard habitats in Slovenia and we discuss factors relevant to their global distribution and relative abundance.
Found in: osebi
Keywords: Wine, microbiome, yeast, Ecology, Fermentation
Published: 12.02.2016; Views: 2547; Downloads: 128
.pdf Fulltext (3,21 MB)

3.
Why, when, and how did yeast evolve alcoholic fermentation?
Jure Piškur, Sofia Dashko, Nerve Zhou, Concetta Compagno, 2014, original scientific article

Found in: osebi
Keywords: kvasovke, evolucija, metabolizem ogljika, alkoholna fermentacija
Published: 09.05.2017; Views: 1979; Downloads: 78
URL Fulltext (0,00 KB)

4.
Introduction to carbon metabolism in yeast
Jure Piškur, Sofia Dashko, Concetta Compagno, 2014, independent scientific component part or a chapter in a monograph

Found in: osebi
Keywords: yeast, carbon metabolism, alcohilic fermentation
Published: 09.05.2017; Views: 1792; Downloads: 12
URL Fulltext (0,00 KB)

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