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Name: Marissa S.
Status: student
Age: 18
Location: N/A
Country: N/A
Date: 2001

Why can yeast rarely produce more than 14% ethanol?

The growth of ethanol-producing yeasts is self-limiting because when the concentration of ethanol reaches about 14% it becomes toxic to the yeast cells.

Vince Calder


Just like with all animals, the alcohol is a toxin. At levels above a certain percentage, this waste product kills the yeast.

Fortunately, at lesser levels, we can enjoy alcohol with apparent health benefits. Naturally, if we consume too much alcohol, the effect on us can be the same as the yeast.

Thanks for using NEWTON!

Ric Rupnik

Ethanol is a toxic waste product. The yeast are poisoned by it.

Richard E. Barrans Jr., Ph.D.
Assistant Director
PG Research Foundation, Darien, Illinois

Dear Marissa,

The alcohol concentration eventually becomes simply too toxic for the yeast to tolerate.

Jeff Buzby, Ph.D.

The alcohol concentration inhibits the function of certain enzymes in the yeast...high alcohol concentration becomes toxic.

Peter Faletra Ph.D.
Assistant Director
Science Education
Office of Science
Department of Energy


You have to remember that the ethanol is a waste product as far as the yeast is concerned. I believe that the ethanol builds up to a point where the yeast can no longer actively grow in the culture (or wine or beer bottle). In effect, they are fouling their own nest.

Paul Mahoney, Ph.D.

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