Published 2 April 2019.
This was written for the 101 section of US beer website, October, to give a brief overview of the subject.
Our single-celled helpers were busy doing us a solid on the regular long before we doltish humans even knew that yeast existed. Which is just another way of pointing out that not so long ago all beer would have been what we now call spontaneously fermented (“spon” for short) or wild beer.
The article explains who spontaneous beers are made, using coolships and wild yeasts.
When fermentation takes hold, wild Sacch does its usual thing, eating up the short-chain sugars and pumping out carbon dioxide and alcohol. You can think of it like a picky preschooler; it only eats the simple stuff. It leaves behind the complex, long-chain sugars upon which Brett, Lacto and Pedio will chow down once the Sacch has filled its boots.