AUTHOR=David-Vaizant Vanessa , Alexandre Hervé 

TITLE=Flor Yeast Diversity and Dynamics in Biologically Aged Wines

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.02235

DOI=10.3389/fmicb.2018.02235

ISSN=1664-302X

ABSTRACT=<p>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, <italic>S. cerevisiae</italic>. Scanning electron microscope observations of these velums revealed unprecedented biofilm structures and various yeast morphologies formed by the sole <italic>S. cerevisiae</italic> species. Our results highlight that different strains of <italic>Saccharomyces</italic> are present in these velums. Unexpectedly, in the same velum, flor yeast strain succession occurred during aging, supporting the assumption that environmental changes are responsible for these shifts. Despite numerous sample wine analyses, very few flor yeasts could be isolated from wine following alcoholic fermentation, suggesting that flor yeast development results from the colonization of yeast present in the aging cellar. We analyzed the <italic>FLO11</italic> and <italic>ICR1</italic> sequence of different <italic>S. cerevisiae</italic> strains in order to understand how the same strain of <italic>S. cerevisiae</italic> could form various types of biofilm. Among the strains analyzed, some were heterozygote at the <italic>FLO11</italic> locus, while others presented two different alleles of <italic>ICR1</italic> (wild type and a 111 bp deletion). We could not find a strong link between strain genotypes and velum characteristics. The same strain in different wines could form a velum having very different characteristics, highlighting a matrix effect.</p>