I'm late posting this (and it'll be short) as I've been out today: we took my dad to a whisky distillery as another birthday treat! They had a brewery on site so the microbiologist in me was excited!
Breweries use yeast (saccharomyces cerevisiae) to create the alcohol. They do this by feeding them a sugar source, in this case barley grist, and taking away all the oxygen. This makes the yeast stop using the oxygen for respiration so in order to still get energy it ferments the sugars to ethanol, which gives the drinks their alcohol levels. Ethanol does eventually kill the yeast if there's too much of it, which is why you can't get much higher than fifteen or so percent without distilling it!
We saw that process too, with the big fractionation columns, then got to try some of the end product (and even some of the raw 92% stuff!) Which was delicious!
It was a fantastic day, and for me was great to see some friendly microbes being put to good use! Thanks, Penderyn!