What is a kombucha SCOBY? How to grow and store one

A kombucha SCOBY is the symbiotic culture of bacteria and yeast that turns sweet tea into tart, lightly fizzy kombucha. The thick, rubbery disc floating on the brew is not the culture itself but its home: a biofilm made of cellulose produced by acetic acid bacteria. Despite the old nickname “kombucha mushroom”, a SCOBY is not a mushroom at all.

What does SCOBY stand for?

SCOBY stands for Symbiotic Culture of Bacteria and Yeast. The community lives in two places:

• In the liquid. Most of the microbes are suspended in the kombucha itself, which is why mature kombucha works as a starter.
• In the pellicle. The disc on the surface is a mesh of cellulose fibres with bacteria and yeast cells embedded in it.

A new pellicle forms at the surface with every batch, either fusing onto the old one or growing as a separate layer. That is why homebrewers quickly end up with a stack of “baby” SCOBYs.

Why is it not a mushroom?

The confusion comes from looks and from older names like “tea fungus”. Here is what is actually going on:

• The yeasts in a SCOBY are fungi in the microbiological sense.
• The disc you can see, however, is made by bacteria: Komagataeibacter species turn glucose into bacterial cellulose (Su et al., 2023).
• It is unrelated to edible mushrooms; it has no stem, cap or spores and does not grow in soil.

“Kombucha culture” is the more accurate term.

Which microbes live in a kombucha SCOBY?

Every culture is a little different, shaped by the tea, sugar, temperature and the starter it came from. Still, research keeps finding the same core members:

Group	Common genera	What they do
Acetic acid bacteria	Komagataeibacter (formerly Gluconacetobacter / Acetobacter xylinum), Gluconobacter, Acetobacter	Oxidise ethanol to acetic acid and glucose to gluconic acid; build the cellulose pellicle
Yeasts	Brettanomyces (Dekkera) bruxellensis, Zygosaccharomyces, Saccharomyces, Candida	Split sucrose into glucose and fructose; produce a little alcohol and CO₂
Lactic acid bacteria	Lactobacillus and relatives (not in every culture, usually in low numbers)	Produce lactic acid and contribute to flavour

A 2019 PeerJ paper by May and colleagues describes kombucha as a model ecosystem of cooperation and conflict: yeast secrete invertase that makes sugar available to everyone, while the bacterial cellulose biofilm offers the community protection and access to oxygen. A study of 23 kombuchas from across the US by Landis et al. (2022) found Komagataeibacter rhaeticus and Brettanomyces bruxellensis to be the most common microbes, and showed that this yeast paired with Komagataeibacter strains was enough to produce a kombucha with a robust biofilm.

How to make a SCOBY from raw kombucha

You can grow your own SCOBY starter from a bottle of raw, unflavoured, unpasteurised kombucha:

1. Make sweet tea with 1 L of water, 4–5 g of black tea and 70–80 g of sugar; let it cool to room temperature.
2. Pour it into a clean glass jar and add 200–250 mL of raw kombucha. The extra starter drops the pH fast and protects against mold.
3. Cover with a tightly woven cloth and leave it undisturbed at 22–27 °C.
4. Within 3–7 days a thin translucent film appears. Once it is a few millimetres thick, usually after 2–4 weeks, it is ready to use.

Brown, stringy yeast strands at the bottom are normal. For a full first-batch recipe, see how to make kombucha at home.

How to store a SCOBY: the SCOBY hotel

To take a break or keep spares as backup, set up a SCOBY hotel:

• Use a clean, wide-mouth glass jar.
• Stack the SCOBYs and cover them completely with mature, tart kombucha.
• Cover with cloth and keep at room temperature away from direct sunlight.
• Every 4–6 weeks, pour off some liquid and replace it with fresh sweet tea.
• If the liquid becomes very sour (below about pH 2.5), dilute it with fresh tea before using it as starter.

Virginia Cooperative Extension guidance for small producers recommends refrigerating SCOBYs in a cleaned, sanitised, covered food-grade container, submerged in liquid from the previous batch. Many homebrewers prefer a room-temperature hotel because cold slows the culture down. Whichever you choose, the rule is the same: keep the SCOBY submerged in acidic liquid. Freezing or drying weakens the culture.

Healthy SCOBY or mold?

Healthy / normal	Mold or spoilage
Cream, beige or light brown; moist, glossy surface	Dry, fuzzy, raised cotton-like patches
Brown stringy yeast, dark spots	Round blue, green, black or pink colonies
Holes, bubbles, uneven edges	Spots growing on a dry area of the surface
Vinegar and light yeasty smell	Musty, earthy or cheesy off-odour
Thin translucent new layer forming on top	No new growth for a long time and the liquid is not souring

If you see mold, do not try to rinse it off: discard the culture and the liquid, clean the jar and start again. You may also see kahm yeast, a thin white wrinkled film that is not fuzzy. It is generally considered harmless but spoils the flavour and usually signals a weak starter.

Where to get a kombucha SCOBY

• From a reliable supplier. A culture with a known source, produced in clean conditions, is the safest start.
• Grow it yourself from raw kombucha using the method above.
• From a friend. Common among homebrewers, but you cannot know the culture’s history. For commercial producers, Virginia Cooperative Extension advises buying the first culture from a reliable, preferably commercial source and not sharing cultures.

Why commercial brewers rely on starter liquid, not the pellicle

At home the SCOBY gets all the attention. At commercial scale the balance shifts: what really starts each batch is measured starter liquid from the previous batch, typically around 10% of the volume (New York State Department of Agriculture). There are good reasons for this:

• It can be measured. The starter’s pH and acidity are checked and dosed at the same ratio every time. You cannot measure the “strength” of a disc.
• Consistency. Standardised starter gives the same flavour and acidification curve from batch to batch.
• Hygiene and handling. Lifting heavy cellulose mats in and out of large stainless steel fermenters is awkward and a contamination risk. In commercial production the pellicle is mostly removed as a by-product.
• Culture management. Larger producers keep and monitor a mother culture, and some use standardised starter cultures with a characterised microbial make-up.

In our Fethiye brewery we start every batch with a measured starter and track culture health by taste, aroma and pH. For the tanks and culture handling a commercial operation needs, read our guide to commercial kombucha brewing equipment.

The bottom line

A SCOBY is less the heart of kombucha than its house: the bacteria and yeast in the liquid do the work, and the disc is the cellulose they build around themselves. At home you can grow one in a few weeks and keep it alive for years in a SCOBY hotel. If you are planning to brew commercially, our production setup service covers culture selection, starter management, tanks and hygiene planning as part of a turnkey plant.