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IVES 9 IVES Conference Series 9 OENO IVAS 9 Category: OENO IVAS 2019 ( Page 9 )

Proceedings of OENO IVAS 2019

From June 25th to June 28th 2019, the research unit in Enology, ISVV, University of Bordeaux, organized jointly the 11th symposium of Enology, Œno2019 and the 11th edition of In Vino Analytica Scientia IVAS 2019. 

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Grape and wine microorganisms: diversity and adaptationIVES Conference SeriesOENO IVAS 2019

Flor yeast diversity and dynamics in biologically aged wines

Wine biological aging is characterized by the development of yeast strains that form a biofilm on the wine surface after alcoholic fermentation. These yeasts, known as flor yeasts, form a velum that protects the wine from oxidation during aging. Thirty-nine velums aged from 1 to 6 years were sampled from “Vin jaune” from two different cellars. We show for the first time that these velums possess various aspects in term of color and surface aspects. Surprisingly, the heterogeneous velums are mostly composed of one species, S. cerevisiae. Scanning electron microscope observations of these velums revealed unprecedented biofilm structures and various yeast morphologies formed by the sole S. cerevisiae species.

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Grape and wine microorganisms: diversity and adaptationIVES Conference SeriesOENO IVAS 2019

Application of high-throughput sequencing tools for characterisation of microbial communities during alcoholic fermentation

Developments in high-throughput sequencing (HTS) technologies allow us to obtain large amounts of microbial information from wine and must samples. Thus approaches, that are aimed at characterising the microbial diversity during fermentation, can be enhanced, or possibly even replaced, with HTS-based metabarcoding. To reduce experimental biases and increase data reproducibility, we compared 3 DNA extraction methods by evaluating differences in the fungal diversity with Riesling alcoholic fermentation samples at four different vineyards. The fungal diversity profiling was done using the genetic markers ITS2 and D2 using metabarcoding. The extraction methods compared consisted of a commercial kit, a recently published protocol that includes a DNA enhancer, and a protocol based on a buffer containing common inhibitor removal reagents. All methods were able to distinguish vineyard effects on the fungal diversity, but the results differed quantitatively.

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Grape and wine microorganisms: diversity and adaptationIVES Conference SeriesOENO IVAS 2019

Extracellular substances of lactic acid bacteria interests in biotechnological practices applied to enology

Extracellular substances (ECS) represent all molecules outside the cytoplasmic membrane, which are not directly anchored to the cell wall of microorganisms living through a planktonic or biofilm phenotype. They are the high-biomolecular-weight secretions from microorganisms (i.e. extracellular polymeric substances – EPS – proteins, polysaccharides, humic acid, nucleic acid), and the products of cellular lysis and hydrolysis of macromolecules. In addition, some high- and low-molecular-weight organic and inorganic matters from environment can also be adsorbed to the EPS. All can be firmly bound to the cell surface, associated with the EPS matrix of biofilm, or released as being freely diffusing throughout the medium.

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Grape and wine microorganisms: diversity and adaptationIVES Conference SeriesOENO IVAS 2019

New antibacterial peptides produced by Saccharomyces cerevisiae responsible for the inhibition of malolactic fermentation

In winemaking, several antimicrobial peptides (AMPs) produced by different strains of Saccharomyces cerevisiae were found to be responsible for the inhibition of malolactic fermentation (MLF) carried out by some strains of Oenococcus oeni. However, only two AMPs produced by one of the yeast strains studied were totally identified and their mechanism of action was described. In an attempt to identify new AMPs, a 5-10 kDa peptidic fraction produced by an oenological strain of S. cerevisiae and previously shown to strongly inhibit MLF carried out by a strain of O. oeni was further purified.

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