SCOBY is the symbiotic colony of bacteria and yeasts that makes kombucha fermentation possible. It is the "starter" or "mother" that transforms a sweetened tea infusion into a fermented drink packed with probiotics, organic acids, and vitamins. Its name is an acronym: Symbiotic Culture Of Bacteria and Yeast.
What is SCOBY
SCOBY is the biological heart of kombucha. Without it, there is no fermentation, and without fermentation, there is no kombucha. Just as you need sourdough starter to make sourdough bread, or a previous yoghurt to cultivate a new one, to make kombucha you need a starter culture to initiate the process.
That culture is SCOBY: a colony of acetic acid bacteria, lactic acid bacteria, and yeasts that live together in a symbiotic relationship. Yeasts break down sugar into glucose, fructose, ethanol, and CO₂. Bacteria then transform these products into beneficial organic acids. Each microorganism performs a part of the work, and all need each other.
It is also called "kombucha mushroom" or "mother", although technically it is not a mushroom: it is a biofilm formed by bacterial and yeast colonies living within a cellulose matrix.
What a SCOBY looks like
An adult SCOBY looks like a creamy or light beige gelatinous disc, shaped like the container in which it formed. The texture is reminiscent of squid or a jellyfish: firm yet flexible, slightly spongy, and slippery to the touch.
Its typical visual characteristics:
- Colour: cream, beige, light brown. Darker spots or streaks may appear (these are not mould if the texture remains smooth).
- Texture: gelatinous, similar to a compact jelly disc.
- Thickness: from a few millimetres to 2-3 cm depending on fermentation time.
- Smell: slightly vinegary, mild. Never rotten or mouldy.
The SCOBY grows in layers: with each new fermentation, a new layer forms on top of the previous disc. This is why an "old" SCOBY can have several separable layers, sometimes called "babies" of the original SCOBY.
Warning: if fuzzy white raised spots, green, black, or bluish spots appear, or if the smell is unpleasant, the SCOBY is contaminated and must be discarded along with the entire batch.
What a SCOBY contains
The exact microbial composition varies depending on the origin of the culture, but most SCOBYs contain a combination of these families:
Bacteria
- Acetobacter and Komagataeibacter (including K. xylinus): produce acetic acid and the cellulose matrix that gives SCOBY its structure.
- Gluconobacter: converts glucose into gluconic acid.
- Lactobacillus: produces lactic acid.
Yeasts
- Saccharomyces (including S. cerevisiae): primary sugar fermenters.
- Zygosaccharomyces: provides alcohol and acid tolerance.
- Brettanomyces: contributes to complex aromatic profiles.
This diversity is what differentiates an authentic SCOBY from a standardised industrial culture. The more varied the composition, the more complex the profile of organic acids and aromas of the resulting kombucha.
How fermentation works
The SCOBY acts as a small ecosystem. When introduced into a sweetened tea infusion, a two-stage process begins:
Stage 1: Yeasts
Yeasts break down sucrose (common sugar) into simpler molecules: glucose and fructose. From there, they generate ethanol and carbon dioxide. This is the alcoholic phase of fermentation.
Stage 2: Bacteria
Acetic acid bacteria oxidise the ethanol produced by the yeasts and transform it into acetic acid. Other bacteria convert glucose into gluconic acid, glucuronic acid, and lactic acid. This is the acidic phase.
The final result is a drink with very low residual alcohol (below 1.2% in Mūn), rich in organic acids, lightly carbonated, and with a flavour between sweet and sour.
At Mūn Kombucha, we ferment for one month in small batches with our own SCOBYs cultivated since 2015. A long fermentation ensures more organic acids, less residual sugar, and a more complete aromatic profile.
The starter: the other key ingredient
Along with the SCOBY, a little starter liquid is always added: kombucha already fermented from a previous batch. It serves two functions:
- It quickly acidifies the sweet tea to a pH below 4, which protects the mixture from pathogenic bacteria that cannot withstand that pH.
- It provides a dense population of bacteria and yeasts dispersed in the liquid, not just those living within the SCOBY disc.
Without starter, the SCOBY may not initiate fermentation quickly enough, and the batch becomes vulnerable to contamination. Without a SCOBY, the starter alone cannot maintain the culture's structure over time.
Optimal conditions for SCOBY
For the SCOBY to work well and produce good kombucha, it needs:
- Temperature: between 20 and 30°C (ideal 22-26°C).
- Initial pH: below 4 (thanks to the starter).
- Oxygen: fermentation is aerobic; the container should only be covered with a breathable cloth.
- Partial darkness: avoid direct sunlight, which can harm the yeasts.
- Glass container: never metal (except stainless steel). The acid could react with the metal.
- Unflavoured tea: essential oils from flavoured teas can inhibit the SCOBY. Pure green, black, or white tea are the best options.
How to store a SCOBY
If you are not going to use the SCOBY immediately, you can keep it alive between fermentations:
- SCOBY Hotel (recommended): a glass container with starter covering the SCOBY, at room temperature. It can be stored like this for several months.
- Fridge: only for short periods (weeks). Cold slows down the culture but can also weaken it.
- Frozen or dehydrated: not recommended, the SCOBY loses much of its viability.
Where to get a SCOBY
If you want to make kombucha at home, you need to get a quality SCOBY:
- From a trusted home brewer: SCOBYs reproduce, so anyone who makes kombucha has "babies" to share.
- By purchasing from a specialised supplier: there are online stores that ship SCOBYs with starter included.
- By cultivating it from scratch: from an unpasteurised kombucha bought in a shop, allowing it to form its own SCOBY (requires weeks and a truly raw kombucha).
Warning: pasteurised kombuchas are not suitable for cultivating a SCOBY because pasteurisation kills all microorganisms. Ensure that the starting kombucha is raw and unfiltered.
Frequently asked questions about SCOBY
Is SCOBY a mushroom?
No, although it is popularly called "kombucha mushroom". It is a biofilm formed by colonies of bacteria and yeasts living together in a cellulose matrix. Yeasts are single-celled fungi, but the SCOBY as a whole is not a mushroom in the botanical sense.
Can SCOBY be eaten?
Yes, it is edible. Some people add it to smoothies, dehydrate it to make vegan "jerky" snacks, or use it to make vegan leather. Its taste is very acidic and the texture gelatinous, so it is not pleasant to eat on its own.
How long does a SCOBY last?
Indefinitely if cared for properly. As long as it is fed with sweetened tea periodically, a SCOBY can be kept alive for years. In fact, many active SCOBYs today come from cultures passed down through decades.
Why does my SCOBY sink or float irregularly?
This is normal. At the start of a new fermentation, the SCOBY may sink, lie on its side, or float partially. As yeasts produce CO₂, bubbles accumulate underneath and lift it to the surface. It does not affect the quality of the final product.
Can I use a SCOBY multiple times?
Yes, indefinitely. The only thing that changes is that with each fermentation, a new layer forms on top of the previous disc. You can separate the layers (the "babies") and share them or use them to start new batches in parallel.
What if my SCOBY has dark spots?
Small brown spots or dark streaks are normal: they are usually tea residues concentrated in the cellulose matrix. What does indicate contamination is the appearance of fuzzy (white, green, or black) raised spots on the surface. In that case, discard the SCOBY and the batch.
Do I need a new SCOBY for each batch?
No. The same SCOBY can be used for many consecutive batches, and it even increases in size with each one. The important thing is to ensure the addition of starter (fermented liquid) each time.
Can I make kombucha without a SCOBY using only raw kombucha as a starter?
Yes, it is possible. With enough raw unpasteurised kombucha as starter liquid (at least 10-20% of the total volume), a new SCOBY will develop on the surface during the first 2-3 weeks. It requires more time and vigilance.
Does SCOBY contain alcohol?
The SCOBY itself does not contain significant amounts of alcohol. The alcohol produced during fermentation remains in the liquid (the kombucha), not accumulated in the gelatinous disc.
Why is it called "tea mushroom"?
It is a traditional name inherited from ancient Asian cultures that saw the SCOBY as a type of floating mushroom or fungus. Although technically not a fungus, the name has remained in popular language in many languages.
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