• Reduce text

    Reduce text
  • Restore text size

    Restore text size
  • Increase the text

    Increase the text
  • Print

    Print
Wine cellar in the Agronomy and Viticulture Experimentation Unit at the INRA center in Colmar. Opening of a cask used in a microvinification experiment. © INRA, MAITRE Christophe

Yeast: how wines get made

Wine yeasts descended from Mediterranean oak yeasts

We now know the evolutionary origins of wine yeasts—they came from yeasts that live on Mediterranean oaks. At some time in the distant past, these wild yeast species moved from trees to cultivated grapevines and evolved their renowned fermentation abilities.

By Pascale Mollier, translated by Jessica Pearce
Updated on 12/23/2016
Published on 09/28/2016

Dating back to 5500 BC, the earliest traces of winemaking have been found in the country of Georgia, as well as in northwestern Iran. The practice then spread to the west and arrived in Gaul in approximately 600 BC. The existence of wine points to the existence of yeasts capable of fermentation. Therefore, wine yeasts existed on cultivated grapevines at least 5,000 years ago. However, questions abound. Where did these yeasts come from? What was their natural reservoir? Knowing the answers would help scientists reconstruct the genomic steps leading to their domestication and identify the adaptive features associated with alcoholic fermentation. This information is key to breeding new types of wine yeasts.

Saccharomyces cerevisiae contains several groups of strains

Wine yeasts all belong to the species Saccharomyces cerevisiae, whose representatives can be found worldwide on fruit or trees, and on oak trees in particular. Previous studies examining S. cerevisiae diversity have identified several groups of strains displaying varying degrees of genomic similarity. All the oak yeasts collected to date in the United States are similar to sake yeasts, but both these groups are rather different from wine yeasts, which raises interesting questions regarding the latter’s origins.

Wine yeasts come from Mediterranean oak yeasts

. © INRA, ETIENNE Michel
© INRA, ETIENNE Michel

After extensively sampling yeasts from different types of fruit and trees across Europe, Portuguese and French researchers have identified a group of yeasts that are common on Mediterranean oaks. A genomics study showed that these yeasts were very similar to wine yeasts and are likely their natural reservoir.

However, a finer-scale comparison showed that three important genomic clusters that have been described in wine yeasts are absent from Mediterranean oak yeasts. These clusters are characterized by major fermentation genes (1). Consequently, the genes were probably acquired after wine yeasts and Mediterranean oak yeasts diverged, under the influence of artificial selection.

 

A new understanding of how wine yeasts emerged

As a result of this discovery, INRA researchers are trying to recreate the process that led to the evolution of wine yeasts: they are cultivating Mediterranean oak yeasts on grape must over several generations and will use sequencing to help quantify genomic changes and the appearance of adaptations (2). This study will reveal whether artificial selection in the laboratory can produce the same results as historical artificial selection and whether the latter ultimately led to optimal adaptations.

A related study (3) is characterizing ancient yeasts using DNA found on pottery that held wine, the goal being to reconstruct the genetic trajectory leading to modern strains.
 
(1) See article 2 in this report on yeasts and horizontal gene transfer

(2) ANR project: PeakYeast (2015–2020)

(3) ANR project: Viniculture (2016–2021)

Contact(s)
Scientific contact(s):

Associated Division(s):
Microbiology and the Food Chain
Associated Centre(s):
Occitanie-Montpellier

Reference

Almeida P, Barbosa R, Zalar P, Imanishi Y, Shimizu K, Turchetti B, Legras JL, Serra M, Dequin S, Couloux, A, Guy, J, Bennasson, D, Goncalves P, Sampaio JP. 2015. A population genomics insight into the Mediterranean origins of wine yeast domestication. Mol Ecol. 24:5412–27.

Genetic diversity of Saccharomyces cerevisiae

. © INRA
© INRA

Figure showing the genetic diversity present in Saccharomyces cerevisiae, which includes fermenting yeasts (in red), oak yeasts (in green), and fruit yeasts (in orange). Near the bottom of this unrooted tree, the US oak yeasts and sake yeasts are clustered together, underscoring their genetic similarity. At the top of the tree, the wine yeasts are found near the European oak yeasts.

The oak and the grapevine

Oaks not only harbored the ancestors of wine yeasts, they also furnish the wood from which wine barrels are made. This use dates back to the time of the Gauls. The wood is heated to bend it to form the barrel, releasing vanillin, a compound responsible for sweet aromas.