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3. 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: osebi
Ključne besede: Yeasts, biodiversity, molecular biology, alcoholic fermentation
Objavljeno: 02.11.2015; Ogledov: 6546; Prenosov: 131
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4. Changes in the relative abundance of two Saccharomyces species from oak forests to wine fermentationsJure Piškur, Justin C. Fay, Lorena Butinar, Sofia Dashko, Helena Volk, Ping Liu, 2016, izvirni znanstveni članek Opis: 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.
Najdeno v: osebi
Ključne besede: Wine, microbiome, yeast, Ecology, Fermentation
Objavljeno: 12.02.2016; Ogledov: 4232; Prenosov: 171
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5. Pre-flowering leaf removal alters grape microbial population and offers good potential for a more sustainable and cost-effective management of a Pinot Noir vineyardPaolo Sivilotti, Lorena Butinar, Melita Sternad Lemut, Jana Laganis, Urška Vrhovšek, 2015, izvirni znanstveni članek Najdeno v: osebi
Ključne besede: kontrola mikrobne infekcije, gospodarjenje z vinogradom, odstranjevanje listov pred cvetenjem, trajnostno vinogradništvo
Objavljeno: 16.06.2016; Ogledov: 4047; Prenosov: 123
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7. 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: osebi
Ključne besede: wine, Vitis vinifera L. cv. ‘Pinot Noir’, biodiversity, yeasts, fermentation
Objavljeno: 10.07.2017; Ogledov: 4194; Prenosov: 198
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8. Alternativne vinogradniške in vinarske tehnologije: kakovostni, trajnostni in senzorični potencialUrška Vrhovšek, Jana Laganis, Lorena Butinar, Paolo Sivilotti, Melita Sternad Lemut, 2017, objavljeni povzetek znanstvenega prispevka na konferenci (vabljeno predavanje) Najdeno v: osebi
Ključne besede: odstajevanju listov v predelu grozdov, trajnostno vinogradništvo, Botrytis cinerea, mikrobna ekologija vinske trte, alternativne vinarske tehnologije, senzorika vina.
Objavljeno: 29.06.2017; Ogledov: 3499; Prenosov: 165
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10. Combined effects of early season leaf removal and climatic conditions on aroma precursors in ‘Sauvignon blanc’ grapesAndreja Vanzo, Paolo SABBATINI, Klemen Lisjak, Marijan Bubola, Melita Sternad Lemut, Lorena Butinar, Branka Škvarč, Jose Carlos HERRERA, Rachele FALCHI, Paolo Sivilotti, 2017, izvirni znanstveni članek Opis: Early leaf removal around the cluster zone is a common technique applied in cool climate viticulture, to regulate yield components and improve fruit quality. Despite the increasing amount of information on early leaf removal and its impact on total soluble solids, anthocyanins and polyphenols, less is known regarding aroma compounds. In order to verify the hypothesis that defoliation, applied before or after flowering, could impact the biosynthesis of thiol precursors, we performed a two year (2013 and 2014) experiment on Sauvignon blanc. We provided evidence that differential accumulation of thiols precursors in berries is affected by the timing of defoliation and this impact was related to modifications in biosynthetic pathway. Furthermore, the possible interaction between leaf removal treatment and seasonal weather conditions, and its effect on the biosynthesis of volatile precursors are discussed. Our results suggested that in Sauvignon blanc the relative proportion of 4-S-glutathionyl-4-methylpentan-2-one (G-4MSP) and 3-S-glutathionylhexan-1-ol (G-3SH) precursors can be affected by defoliation, and this could be related to the induction of two specific genes encoding glutathione-S-transferases (VvGST3 and VvGST5), while no significant effects on basic fruit chemical parameters, polyphenols and methoxypyrazines were ascertained under our experimental conditions.
Najdeno v: osebi
Ključne besede: early leaf removal, cluster exposure, thiol precursors, methoxypyrazines, glutathione S-transferase, Vitis vinifera
Objavljeno: 31.08.2017; Ogledov: 3172; Prenosov: 0
Polno besedilo (1,04 MB) |
