It’s no secret that some of our favourite foods are the handiwork of microbes. Cheeses, breads, beers, yoghurts, pickles – maybe even truffles – all owe their distinctive characters to invisible bacteria, yeasts, and other fungi. Some foods rely on the critters that just happen to be in the vicinity – kimchi fermentation, for example.

But many involve microbes grown on an industrial scale by specialised companies. These bugs are the world’s tiniest farm animals, in a sense – hundreds of thousands of tons of them are reared every year. To learn more about the process, I spoke to Karen Fortmann, a post-doctoral researcher who works at White Labs, a company that cultivates the brewer’s favourite friend: yeast.

The first thing to know about these industrial cultures is that some of them are ancient. Companies store their stock in freezers, the microbial equivalent of cryogenic freezing. Fortmann says that some of White Labs’ strains are much older than even the company, which has been around for 20 years. To produce yeast for clients to use, they thaw a thimbleful of the creatures and feed them on a malt-based solution, moving them into larger receptacles as they multiply.