Yeast’s struggle to survive makes wine making possible

August 5th, 2008 - 12:55 pm ICT by IANS  

Sydney, Aug 5 (IANS) Researchers studying yeast discovered that the process that turns grape juice into wine also helps the yeast to survive and obtain essential nutrients from the fruit. They studied the microbes present on grapes from the field to the cellar and discovered the presence of a few Saccharomyces cerevisiae, the yeast required to convert sugar to alcohol.

However, it created a warm, high alcohol in a low oxygen environment which is toxic to all other yeasts and microbes during the fermentation process, allowing its numbers to rapidly increase.

This environmental-engineering is wasteful for the yeast, as it is more efficient to completely metabolise the fruit sugar into water and carbon dioxide, but the fermentation releases ethanol and heat and ensures S. cerevisiae’s survival.

“Environmental engineering is a known concept, originally described by Darwin,” said Mat Goddard of the School of Biological Sciences.

“However, while many organisms modify their environment - think of beavers building dams - the evolutionary effect of this has never been measured before. In the case of winemaking, it seems ‘Natural Selection’ has caused yeast to adapt to change its environment to create a competitive advantage over other microbes in the niche.”

The results were published in Ecology.

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