Saturday 23 August, 2014

Beer-brewing yeast found

Published On: Wed, Aug 24th, 2011 | Biology | By BioNews

Scientists have identified a new species of yeast from forests in South America that was behind the discovery of lager, a type of beer brewed and stored at low temperatures.

The species was isolated from a beech tree in the frozen forests of Patagonia, where the minimum temperature hovers around minus-2 degrees Celsius, BBC reported.

The new yeast species has been named “Saccharomyces eubayanus”, says the report in the Proceedings of the National Academy of Sciences.

Usually, the yeast Saccharomyces cerevisiae is used across the world to ferment fruit and grains to make wine, cider and beer.

Lager – which is fermented slowly and at lower temperatures than beer – is believed to have been discovered when German monks moved beer barrels into caves to store it.

Saccharomyces cerevisiae, which grows just above room temperature, was believed to have been out-competed in the fermenting beer by a species that thrived at cooler temperatures.

The “modern-day” lager-brewing yeast – Saccharomyces pastorianus – is probably a hybrid of this “cool-loving strain” and the beer-brewing species, and survives because brewers keep back a little of the lager each time to develop the next batch with the same yeast, the report said.

“The hybrid almost definitely formed accidentally and people adopted it because the beer came out differently,” evolutionary biologist Chris Hittinger from the University of Wisconsin in Madison, US, who was part of the team behind the discovery, was quoted as saying.

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