guys i stuck in one question. the product of alcoholic fermentation ethanol,is lethal to yeast.if the presence of ethanol is harmful to yeast,explain how alcoholic frmentaion can be beneficial to these organisms?

The fermentation doesn't happen because the yeast wants to make ethanol. It happens because it needs energy (which it gets from the sugars and such), ethanol is just one of the waste products. And waste products leave an organism's body for a reason. Mammals breathe air, and expel carbon dioxide, which is very toxic to them. It's not very healthy to swim around in one's own feces or urine either, which is sort of an analogue to ethanol concentrations rising in the yeast's environment.

However, ethanol fermentation does not generate ATP per se, but something different.

The yeast used (in wine making as an example), saccharomyces cerevisiae, is more tolerant to the levels of alcohol produced. So it's growth isn't effected like many other microorganisms would be.

 

At least this is the explanation at A Level. Hope it helps!

True, that might be a school answer. Only it does not make much of a sense as basically any organism can be considered ethanol tolerant. A number of bacterial ethanol fermenters are not noticeable more (and sometimes even less) resistant than others living in the same habitat.

 

The point is that it is basically only a matter of concentration (and the flux in the given habitat).

If it's a matter of concentration then couldn't it be that different microorganisms can tolerate different concentrations?

 

It's the only answer given at A Level. I'd be surprised if someone sitting degree level would be asking the question(?)

there are some awesome strains of Saccharomyces (my favorite animal) out there, that will not only produce alc to nearly 30%!!! but do so in matter of a few days

 

it doesn`t taste particularly nice, but it is potable.

I think that home brewers also realise that the ethanol tolerance of a specific yeast can be slowly increased by slowly adding more sugar once the initial tolerance level has been reached. This indicates to me that alcohol tolerance is increased by training and gradual increments......any drunk can confirm that!!!

 

Look to the humble yeast and learn his ways, oh ye mighty.

Isn't the poster asking how alcohol fermentation is beneficial to the yeast? It allows the yeast to survive(for a while at least) in anaerobic conditions. Analogous to lactic acid in humans.