You do it, I do it, and the Yeast in this Beer Definitely Does it: Fermentation

Today has been ridiculously busy, so on this, Day 6 of 30 Days Wild, the closest I’m getting to wildlife is drinking it. But actually that’s pretty close.

Wild Beer - 30 Days Wild Day 6

Here’s a great beer from one of my favourite companies. It’s brewed using a strain of yeast called Brettanomyces, which produces beer with a fresh, slightly acidic character. It’s a wild yeast whose natural habitat is fruit skins, so it gives us wine and cider as well as beer. I once met a brewing enthusiast who described ‘Brett’ (as it is often called) as “The brewery equivalent of athlete’s foot”, probably because there’s lots of it in the atmosphere and it has a habit of making its way into brews where it isn’t welcome.

Yeast is of course a fungus (more about that in future blog posts), and it produces alcohol through the process of fermentation. Essentially, fermentation is a type of metabolism which occurs in the absence of oxygen. In fermentation, the organism breaks down sugars and converts them to energy plus a number of by-products, one of which can be alcohol.

Brewers use different kinds of yeast depending on which by-product is required. If you’re brewing lager, for example, you’ll want to use a yeast which produces a lot of alcohol. Our pal Brett isn’t such a yeast; when Brett ferments, it produces a small amount of alcohol and a larger amount of lactic acid, which is precisely what gives Brett beers their fresh, lemony character.

It’s also what Brett has in common with humans. We produce lactic acid through fermentation, too: whenever you do intense exercise and start to feel that burn in your muscles, it’s because you’ve been fermenting. We produce tiny amounts of alcohol in our intestines, as well, but that’s because we have small amounts of yeast there.

Sometimes, people even produce a lot of alcohol. There’s a rare medical condition called Auto Brewery Syndrome, where an overgrowth of gut yeast results in just that. When the amount of yeast in the gut is large enough, sufferers can get drunk just by eating starchy food. This proves—if further proof were needed—that the wildlife inside us can be as important as the wildlife on the outside.