What liquid culture is
Liquid culture, usually shortened to LC, is mycelium growing in a sterile nutrient broth instead of on a solid surface. The broth is simple: water with a small amount of sugar, typically light malt extract or honey at about 4 percent by weight, so roughly 40 grams per litre. Some vendors add a little peptone or yeast extract for nitrogen. The mix is sterilised in a pressure cooker, cooled, and inoculated with a wedge of clean mycelium from an agar plate.
Over one to three weeks the mycelium grows into the broth as white strands, clumps and threads. The result is drawn into syringes, usually 10 or 12 ml, and sold as a ready-to-use culture. Because the jar is liquid, a single wedge can be expanded into hundreds of syringes, and because the mycelium is already alive and growing, it colonises grain much faster than a spore print or swab would.
On Culture Cave, liquid cultures are the most common format for gourmet species. Spore syringes are a different product: a suspension of spores in sterile water, sold for microscopy and taxonomy rather than for growing. The differences are set out in spore syringe vs liquid culture.
The stir bar and why it matters
Most LC jars contain a small magnetic stir bar, a short rod coated in PTFE. Set the jar on a magnetic stirrer and the bar spins, breaking the mycelium into small pieces and keeping the broth moving. There are two reasons for this.
First, mycelium left alone forms a single floating mat or a dense ball. That is hard to draw into a syringe and colonises grain slowly because there are few growing tips. Stirring chops it into many small fragments, each of which becomes a new growth point. Second, moving broth keeps oxygen and nutrients evenly distributed, so the culture grows faster and more evenly.
A stirrer is not essential. Swirling the jar by hand once a day works, and some growers shake the jar hard before drawing syringes. But a stir plate makes better, more consistent LC, and most vendors who sell it use one. Stir plates and stir bars are listed under lab equipment.
How to inspect a liquid culture syringe
Hold the syringe up to a window or a lamp and look through it. Good LC has these features.
- Clear broth. The liquid between the mycelium should be transparent, pale straw or light amber depending on the sugar used. You should be able to read text through it.
- White mycelium. Strands, flakes or small clumps that are clean white. They may settle at the bottom or float. Shake the syringe and they should disperse.
- No smell. If you push out a drop onto a clean plate, it should smell faintly sweet or of mushrooms, or of nothing at all.
Signs of trouble are just as clear.
- Cloudy or milky broth. Uniform cloudiness that does not settle is almost always bacteria. Healthy mycelium does not make the liquid opaque.
- Coloured broth. Yellow, green, pink or grey tints, or dark sludge, point to mould or bacterial growth.
- Sour or rotten smell. Bacteria produce acids and gas. A sour smell, or a syringe where the plunger has pushed itself back, is a syringe to throw away.
- Slime. Stringy, snotty material rather than defined strands.
Looking alone is not proof. Low levels of bacteria can hide in LC that looks fine, which is why the agar test below matters.
Storage and shelf life
Keep LC syringes in the fridge at 2 to 4 degrees Celsius, capped, with the needle removed and stored separately in its sterile wrap. In the fridge, liquid culture stays usable for three to six months. Some strains will go longer, and some, particularly lion's mane, slow down and lose vigour sooner.
At room temperature the mycelium keeps growing. Within a few weeks it will have eaten the sugar in the syringe and started to starve. It also produces gas as it grows, which can push the plunger out. If a syringe arrives in the post and you cannot use it straight away, put it in the fridge the same day.
A jar of LC, as opposed to a syringe, keeps a little longer because there is more broth to feed on. Kept cold and stirred occasionally, a jar can hold a strain for six months or more, but the safer practice is to go back to a plate and make a fresh jar rather than keep drawing from an old one.
How vendors test LC before selling
A serious vendor does not sell LC straight from the jar. Before a batch is drawn into syringes, a small amount is dropped onto a sterile agar plate and left at room temperature for five to seven days. Clean LC produces white mycelium spreading from the drop and nothing else. Bacteria show as wet, shiny patches around the drop within two or three days. Mould shows as coloured spots.
Many vendors also keep the mother jar for a further week after drawing syringes, so that any slow-growing contamination shows before customers are affected. Ask a vendor whether they agar test their LC. The good ones will say yes without hesitation, and some show the test plates on their store page. The vendor guide covers what else to ask.
Confirming cleanliness yourself
You can run the same test at home, and you should if the LC is going into expensive substrate. Working in a still air box or in front of a flow hood, wipe the syringe port with alcohol, fit a sterile needle, and put a single drop in the centre of an agar plate. Seal it, label it, and give it a week.
If the plate grows clean white mycelium, the LC is clean and you can use the rest of the syringe with confidence. If anything else appears, do not use the syringe. The plate has cost you very little and saved you a bag of grain. The agar plates guide explains how to read what you see.
Using liquid culture on grain
LC is normally injected into sterilised grain through a self-healing injection port or a filter-patch bag. Two to four millilitres is enough for a bag of 1 to 1.5 kilograms. Spread the liquid around several points rather than one. Because the mycelium is already active, colonisation is visible within three to five days and a bag is usually fully colonised within two to three weeks, depending on the species and temperature. The process is covered in grain spawn and grow bags explained, and sterilised grain itself is listed under substrate and grain.
Gourmet species commonly sold as LC
Almost every culinary and medicinal species sold on Culture Cave is available as liquid culture.
- Oyster mushrooms: blue, pearl, pink, golden and phoenix. Fast, forgiving and the usual first choice.
- Lion's mane: slower and wispier in LC, so expect less visible mycelium in the syringe than with oyster.
- Shiitake: a wood lover that does best on supplemented hardwood sawdust.
- King oyster: thick, meaty stems, grows well on sawdust blocks.
- Chestnut mushroom (Pholiota adiposa): clusters on hardwood, good flavour.
- Reishi: grown for its woody conk and used for extracts.
Browse the full range under gourmet cultures, where each listing shows the species, the vendor's country, shipping regions and customer reviews. Vendors keep 100 percent of each sale, so the price you see is the price the maker set.