The unlikely joy of a SCOBY as a pet

Why a symbiotic culture of bacteria and yeast may be a worthy addition to your household.

Welcome to the weekender, a weekend edition of plus/minus where I turn attention to something more leisurely, like food, sport, or culture.

Photo by Tim-Oliver Metz on Unsplash

This week I returned to Seattle after some time away, and the first thing I checked in on was a large mason jar in my kitchen which houses sugary liquid and a thick, jelly-like blob known as a SCOBY: a symbiotic culture of bacteria and yeast. More specifically, this is a SCOBY designed to create kombucha, a fermented tea with Chinese origins that is increasingly popular in the west.

Bacteria, yeast, and moulds are collectively responsible for an enormous array of food beloved around the world. They’re especially good at boosting the flavour of ordinarily bland ingredients: helping to transform cucumbers into sour pickles, soy beans into umami-packed soy sauce and miso, and milk into salty aged cheese. But microbes have also long been used to ferment liquids into effervescent, often bracing drinks. Among these are familiar alcoholic tipples: beer, wine, and cider are the products of harnessing microbes to turn sugar into alcohol. Alongside booze is another group of fermented drinks, which ur-fermenter Sandor Katz calls “sour tonic beverages”, that depend on a symbiotic culture: a culture of bacteria and yeast, yes, but one which also implicates humans.

Each of these sour tonics, including kombucha but also milk kefir, water kefir, and vinegar, relies on its own kind of SCOBY, which come in all shapes and sizes. For kombucha, this takes the form of a microbial “mat” which is stored in sugar solution as in my mason jar. Making vinegar often involves a so-called “mother of vinegar” (MOV) which, like a kombucha SCOBY, takes the form of a gelatinous disc. Milk kefir and water kefir have no biological relation, but they are namesakes because their SCOBYs each resemble spongy, grain-like cubes which are also stored in sugar solution.

What these SCOBYs have in common, in all their weird and wonderful forms, is that they are living cultures whose survival and growth depends on constant replenishment. Unlike plants or animals, this growth is exponential and continuous, rather than seasonal or generational. SCOBYs don’t reproduce as such, they just continuously and exponentially expand given the right conditions. If they are divided or cut (to be given away), the separated cultures continue to grow by themselves. Yet if they are neglected, they die an ironic death, pickling and putrefying in the very acidic solution that they created.

So what do SCOBYs do? They provide the microbes needed to turn very basic ingredients—usually just sugar, water, and optional flavourings—into delicious and potentially quite healthy drinks.¹ How does this work? It’s pretty simple: you make a sugar or sugary tea solution, add your SCOBY, leave it at an ambient-to-warm environment for anything from a few hours (as with milk kefir) to a few months (as with vinegar), then strain and bottle the resulting brew. (The excess liquid culture can even be used for other ferments, such as sauerkraut or vegan cheese.) You then repeat the process with the same (now larger) SCOBY and a new solution. The precise details—flavouring, timing, temperature—vary based on the SCOBY used and the desired result, but the basic rhythm is the same, and maintaining that rhythm, and sustaining the microbial culture that drives it, is oddly cathartic.

In the scheme of things, caring for a SCOBY is a low-stakes endeavour. (Nobody died of thirst from failing to obtain kombucha.) But as I’ve found through various adventures in foraging, growing, and fermenting food in recent years, it’s precisely these sorts of nutritive experiments that give the space to explore alternative infrastructures for food production and distribution more broadly. Assuming some basic equipment and ready access to sugar and water, you have a theoretically limitless supply of your chosen tonic in exchange for a few minutes of your time every day or two. As a result, the exponential growth of well-tended SCOBYs upends notions of scarcity and abundance. You soon find yourself with much more SCOBY than you need, and before long you’re beseeching bewildered friends to try a fizzy, funky drink they’ve never heard of in the hopes that they’ll take a chunk of starter culture off your hands (my success rate is surprisingly high). And the fact that kombucha, water kefir, and milk kefir are heritage cultures that come from somewhere² means that your SCOBY likely belongs to a lineage dating back centuries and stretching across continents.

For those with beloved pets or house plants (or for that matter children), a SCOBY isn’t going to replace them anytime soon—though the logic of exponentials means it could ultimately outgrow them. But for those who want a low-stress, highly rewarding addition to your household, I highly recommend bringing a friendly envoy from alternative biological kingdoms into your care.±

1. I say “potentially” healthy because the levels of alcohol, sugar, and gut-friendly microbes vary considerably in each batch. As such, these should not be thought of as health drinks—but as I hope this piece has showed, they could perhaps be thought of as an aid to wellness in a broader sense.

2. Nobody is quite sure, but kombucha may have originated in China, water kefir in Mesoamerica and/or eastern Africa, and milk kefir in the Caucasus. By contrast, vinegar is far too ubiquitous and spontaneous a fermentation to have originated anywhere in particular. But this does not mean that you cannot create vinegar lineages. I snagged the leftover red wine from my wedding and a resultant “wed wine vinegar” is happily acidifying on my bookshelf.