Originally Posted by debthecook
Whats that about the alcohol???, I thought your questions were about yeast in breadmaking.
Yeast, all yeast, do indeed feed on sugar. (Some specialized strains can feed on more complex forms of sugar) There are other nutrient requirements as well, but unless you need a ton of sugar converted, it's not an issue.
As the yeasts eat the sugar, the do indeed give of CO2 and alcohol. If you bake it, the trace alcohol goes away. (Lifter's explanation was spot on, except that it's CO2 and not O2)
HOWEVER, add it to beer/wine, and you have the mechanism by which fermentation is achieved. Brewers (and to a lesser extent, vinters) have to take very good care of their yeasts, or any number of bad things will happen (including unsellable beer - bad for business).
As an aside, if you were to put a pound of sugar in a gallon of water, you'd get a alcoholic beverage of about 4-4.5 percent alcohol by volume. Actively fermenting yeast are also how beer and champagne first got their bubbles.
Sheesh! Do I sound like I need to get out of the lab more often, or what?