Starting a new kombucha culture from a bottle of kombucha

We get asked a LOT:

Can we buy cultures from you?

Can we start a culture from a bottle of your kombucha? If so, how?

Short answer to both:

We use to sell kombucha cultures, but we basically stopped because we don’t think there’s much point to cut up and package pieces of the solid mass that floats on top of a kombucha ferment when it is so easy to start a new culture from a bottle of “real” kombucha. All you need is a bottle of quality, unfiltered, unpasteurized kombucha. We have instructions and a video here.

Longer, and hopefully more interesting, answer:

To answer these questions it would help to know what we mean by the word ”culture” when we talk about kombucha. For a bit more detail on that check out our FAQ and blogpost(coming soon) ”What is a culture”, but the short answer is that a “culture” is a dose of sufficient microbes (bacteria and yeasts) and sufficient liquid to establish a new kombucha fermentation. The floating mass that forms on top of a kombucha ferment is primarily layers and layers of cellulose made by Komagataeibacter bacteria in which this bacterium and many other bacteria and yeasts live. It goes by many names, such as ”culture”, ”scoby” (acronym for Symbiotic Culture Of Bacteria and Yeasts), ”mother”, and ”mushroom”. (This last one bothers Nick, the microbiologist at Roots, to no end, since, as he always reminds us, it’s definitely not a mushroom.) Nick, and seemingly few other people, likes to call it a ”pellicle” (“ytkultur” på svenska) because that’s probably the right technical term, but even he calls it a mother, a culture, or a scoby (but not a mushroom!!). This floating mass of cellulose can be used to start a new culture and is the most common way people have handed down the kombucha culture to others, but a piece of this mass alone may not be enough to start a new kombucha culture; it should really be given with some of the liquid. In fact, you really do not need any bit of the pellicle to start a new culture; the liquid is more important. What you need, is the right microbes and some acidic liquid to reduce the pH of the starter culture, and both of these are achieved with just a few dl (about a bottle) of real kombucha. You can and we have heard plenty of stories of people starting cultures with much less, but your chances of starting a good culture rise significantly if you use more kombucha to start your batch. (We have had a video and instructions on the internet on how to start a culture from a bottle of kombucha since 2014, and we are super proud that hundreds if not thousands have watched/read it and used it, and often our kombucha, to start their own cultures at home.)

To be clear, that cellulosic pellicle DOES contain lots, and potentially all of the bacteria and yeasts essential to kombucha fermentation, but transferring a piece of this pellicle WITH the liquid will ensure that you transfer a sufficient dose of the microbial community to start a new fully functional kombucha culture. Depending on the size of the ”piece”, using it alone decreases your chances of starting a new culture, because to get a good start to your kombucha fermentation it’s important to reduce the pH quickly.

Why is it important to acidify your kombucha fermentation?

Kombucha microbes are all acid-tolerant and likely acid-loving microbes; they thrive below pH 4 (for reference: lemon juice 2.3; coca cola 2.5; kombucha 2.7-3.5; apple juice 3.6; tomatoes 4.5; coffee 5), while many other microbes do not. Reducing the pH quickly makes it much harder for other potential contaminating microbes to establish. With microbial growth, the most fit often win, but speed counts, so giving your chosen microbes a head start helps ensure that a mold or bacteria spore that floated in on a piece of dust doesn’t have a chance to get started. Giving them a headstart involves both introducing a big dose of the desired microbes and establishing the right environmental conditions for them to thrive right away. The habit of transferring about 10% of finished kombucha with each new brew rapidly reduces the pH as well as introduces a healthy dose of kombucha microbes, and this is part of why kombucha is such an easy and resilient ferment for home fermenters to work with.

Is a culture started from a bottle different than a culture started from a piece of the pellicle?

We know it works very well to start a culture from our kombucha because we have seen the pellicle form spontaneously hundreds of times on the top of kombucha in our brewery and in most bottles of good kombucha. We have also tested it many times in more household-sized jars of 3 -10 liters. Recently we decided to do a small comparison of the development of culture and flavor between batches of kombucha started side-by-side from bottles of our kombucha, bought off the shelf after a couple months cold storage, or directly from cuttings from one of our mother cultures. That’s documented here, but the results could be summarized as: The pellicle on top grew faster and thickened more rapidly on top of the jars that were started with large pieces of pellicle, but there was little to no difference in liquid pH or kombucha flavor after 4 cycles of fermentation (~6 weeks total). After a time (5-6 fermentation cycles, ~12 weeks) there was no observable difference in culture appearance between the cultures started from a bottle of refridgerated kombucha or the one started from a fresh piece of mother culture and fresh brewed kombucha.

How can that be? Don’t the microbes die off over time? We interpret these results and our many years of experience at home and at Roots observing how cultures grow, develop, and behave to indicate that the majority of the bacteria just slow down, and among those that may die more rapidly, enough remain, that, when given new nutrient and energy sources they quickly get back to work doing what they do, together, in symbiosis. These cultures are amazingly resilient. The kombucha microbes can just chill in their liquid, in some kind of stasis, for a long, long time.

But I’ve read otherwise on other pages?

There is apparently a lot of stuff on the internet that some of the above discussion would seem to contradict. Our fans and others have repeatedly both pointed us to these claims and used us as references in the discussion threads (which we are flattered by). While we are flattered to get pulled in as a reference, we have mostly avoided getting involved. That being said, some of these claims are misleading and confusing, and we’d like to take a moment to address a couple statements made by others that people have brought to our attention a few times now that contrast with that we have said.

Claim: If your kombucha has been sitting for too long, or you rest it for an extended period in the fridge, then you’ve lost valuable microbes and your culture is damaged in some way (and you should get a “new” one).

Correction: We think this is untrue, and possibly a way to get people to buy more cultures. As we have stated above, we, at home, and at Roots, have used cultures stored in the fridge for many months, many times to start cultures, and it works, and generates a culture indistinguishable in behavior from the starter culture. This is common practice amongst kombucha brewers, and based on thousands and thousands of periods of rest, the general consensus is that extended periods in its own liquid at cool temperatures do not “harm” or even significantly alter the kombucha culture. Thinking about it more deeply, the fact that the kombucha culture persists in this fashion means it must have, many, many, many times in the history of its existence. Kombucha has been around for probably well over 2000+ years and has been popular for centuries in places with long cold winters, so it is likely that many many cultures were for long periods of time in their liquid in a cold environment. Thus it seems highly unlikely that storage of kombucha is such a microbial population filter that ”damages” the community composition and function in some way (as some claim).

Claim: Store-bought kombucha can’t be used as a culture source, they’ve industrialized their process so much that it’s not the same kombucha.

Correction: There could be some truth to this. Some kombucha producers pasteurize their product, or mix a very strong kombucha concentrate (sometimes with an altered microbial community composition) with sweet tea, or (more commonly lately) microfilter their kombucha. These processes likely render a kombucha less or not useable as a culture source. But we (and other producers of good kombucha) make a kombucha that is live and well-brewed. In addition, we have gone back and forth from batch sizes of 3 l exactly as many of you (and us) brew at home, to 25 -1000 l batch sizes, and we can say with all our heart that the size of our production does not reduce the quality of our product, nor it’s propensity to establish new kombucha cultures.