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Patrick Guilfoile: Thank bacteria for flavorful wine

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Those of us who enjoy wine owe a lot to yeast, which do most of the fermentation and produce most of the alcohol found in wine.

Yet bacteria also play an important role in determining the final flavor of wine. In particular, a microbe called Oenococcus oeni (Oinos is Greek for wine) produces many of the distinctive flavors associated with most red wines.

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During winemaking, the yeast die when the alcohol concentration reaches a critical point.

These bacteria then convert the nutrients from the now-dead yeast to other compounds that give wine its full taste and texture.

In addition, these microbes play a key role in reducing the acidity of certain types of wine, giving them their characteristic taste.

Recently, scientists from Spain and Italy conducted a series of experiments to understand some of the details of how this bacterium helps make wine.

They grew and harvested the bacteria, and then broke apart their cells by squeezing them through a narrow hole with 12,000 pounds of pressure.  

Next they isolated the proteins from the cells, separated them on a gel, and cut them out.

Finally, they put these individual proteins in a machine that broke them into small pieces and weighed each fragment.

This allowed them to identify the cellular machinery that was involved in the final stage of winemaking.

They found three several categories of proteins that likely are involved in the process of making wine.

One category were proteins involved in stress response; living in alcohol-soaked vats is a challenging environment, so this was not a surprise.

A second category of proteins was involved in converting components of grapes and yeast to the fruity, nutty, buttery, other flavors in wine.

A third category of proteins was involved in making alcohol, although this is primarily the function of the yeast.

Finally, they compared the identified proteins from this microbe with those of other similar microbes.

This work sheds additional light on the complex process of making wine, and may eventually be useful in helping vintners select the best bacterial strains to produce the desired odors and flavors in wine.

It also provides some appreciation of the complex process involved in converting grapes into the “nectar of the gods.”

More information is available in the article by María de la Luz Mohedano entitled “A partial proteome reference map of the wine lactic acid bacterium Oenococcus oeni ATCC BAA-1163.” in Open Biol. 2014 4, 130154, published 26 February 2014

PATRICK GUILFOILE has a doctorate in bacteriology and is the associate vice president at Bemidji State University.

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