So. What strains of probiotics are in kombucha? What are the kombucha microbes that make your brew so good? And can you change them?
We know that SCOBY stands for “Symbiotic Colony of Bacteria and Yeast”. But which bacteria are doing the work? What is a good scoby yeast? And are all kombucha scobys the same? (hint: they’re not)
For my first translation of a scientific research paper in to plain English, I decided to start with the most recent publication. In June 2015 a paper by Oleg N. Reva and colleagues was published in the journal AMB Express :
This study is super exciting to me because it shows that you can add lactobacillus to your kombucha scoby by brewing with cabbage or kefir. It also explains why different people get such different results with their kombucha – it’s because their scobys are different.
Key take-home points:
- The exact mix of microbes in your kombucha scoby and drink will change if you change the liquid you grow it in.
- Using honey instead of sugar resulted in a more unpredictable mix of bacteria and yeasts.
- Kombucha doesn’t necessarily contain lactobacillus – some scobys do and and some scobys don’t.
- Lactobacillus is a good probiotic, so if you want some kombucha lactobacillus in your brew one way to get it there is to add some minced cabbage to one of your ferments.
Background information about kombucha probiotics:
The researchers were looking to see which bacteria and yeasts are present in kombucha grown in different conditions. They are particularly interested in kombucha’s usefulness as a probiotic, especially as the demand for dairy-free probiotics is growing.
Previous studies had shown:
- Drinking kombucha is likely to have positive health effects, so kombucha has potential as a probiotic.
- Kombucha has a lot of different microbes in it – both bacteria and yeasts – but not all of these can be separated out and grown in the lab. It is impossible to identify those bacteria and yeasts using older laboratory methods.
- New techniques have been developed to help identify those bacteria and yeasts.
- Kombucha scobys from different countries have different microbes in them, although there seems to be a core group of bacteria that is always present.
- Kimchi and traditional Korean fermented soy pastes are similar to kombucha because they are also naturally fermented foods. They have a mix of different microbes in them, which changes depending on the recipe and methods used.
- Unlike kombucha, kimchi doesn’t need a starter for fermentation to happen. The active microbes seem to come from the cabbage and the environment.
What these researchers were investigating in this study:
- They are interested in finding out more about kombucha’s usefulness as a probiotic.
- They wanted to know the types of probiotics in kombucha
- They wanted to know how different recipes would affect the population of microbes is in the kombucha scoby and drink.
- They wanted to see if the kombucha scoby would use any fermenting microbes from cabbage, the same way that kimchi does, and if those microbes would stay in the scoby for multiple generations.
What they did:
The researchers took a single kombucha scoby, from the Ukraine, and split it into 4 identical scobys.
They then set up 4 different recipes:
Ordinary black tea plus white sugar. This is the standard recipe that most people use to brew their kombucha.
Sterilized black tea plus white sugar. Sterilizing the black tea means that there are no microbes being added to the mix from the tea leaves themselves. All the microbes they found will have come from the scoby itself.
Ordinary black tea plus honey. Whether you can use honey to grow your kombucha is a question that people often ask. As far as I know, this is the first study to investigate how honey changes the scoby.
Ordinary black tea plus cabbage juice plus honey. This was to see if any of the bacteria that help to ferment kimchi would become part of the scoby. After one week growing in the cabbage juice mix, they removed the daughter scoby and grew it in ordinary black tea plus honey. They tested this scoby after 5 more generations growing it in black tea and honey, to make sure there was no trace of cabbage juice left in the drink.
After brewing each batch of kombucha for 2 weeks, they measured the number and type of bacteria and yeast present in each scoby. For the recipe where they added the cabbage juice they tested the liquid as well as the scoby.
They measured the number and type of microbes by using new DNA sequencing methods that don’t need you to be able to separate out each microbe type in the lab.
What they found: different kombucha microbes
Each of the four recipes produced a different mix of microbes.
There seem to be a common core of bacteria that are present in all kombucha scobys – these are mostly acetobacteria, which produce acetic acid and cellulose (the rubbery stuff the scoby is made from). There is also a handful of yeast species that are usually present, although the kombucha yeast species are much more variable than the bacteria. Other bacteria and yeasts are also present.
The recipe using honey produced the biggest change to the number and type of bacteria present – probably due to honey’s antimicrobial properties.
The recipe with the cabbage showed that lactobacillus (the microbe that ferments kimchi) did transfer from the cabbage juice to the scoby, and continued to be a significant part of the scoby population from then onwards. Lactobacillus wasn’t in any of their other scobys.
So what does that mean for us?
Basically this means that your scoby is not the same as my scoby, and so your kombucha will not be the same as my kombucha. It will be broadly the same, but not identical.
What each of these many different bacteria and yeast do within the scoby, how they interact with each other, and their impact on the healthfulness of the drink is not well understood. It is possible that different batches of kombucha, produced with different recipes, will have different health effects.
If you want to add lactobacillus to your kombucha so that it is a lacto-fermented drink, it will probably be a better probiotic. You can do this by adding some minced cabbage to a batch of kombucha as I describe here. I wouldn’t drink that batch, myself, but the next one should be fine, and the scoby should be lacto-fermenting, as well as acetic-acid-fermenting from then on.
Probably don’t use honey. The antibiotic properties of honey seem to mess with the scoby in quite unpredictable ways. (2018 edit to add: see this article about using different sugars for kombucha that I later wrote in the light of newer research, that talks about using honey and other alternative sugars, and how to get the best results with them).
N.B. Nothing on this website constitutes medical advice. Please consult your doctor for health care.
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