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How to Use Liquid Culture Medium — Step-by-Step Guide

How to Use Liquid Culture Medium — Step-by-Step Guide

Spores · Mycology · Cultivation

Turn your spore vial or spore syringe into fresh liquid culture — faster colonisation, cleaner grows. A Liquid Culture Growth Medium vial is a pre-sterilised nutrient broth in a sealed, ready-to-inoculate vial. Add a small amount of your spore solution, incubate for one to two weeks, and you have a jar full of live mycelium ready to inoculate grain or substrate.

What is liquid culture medium?

A liquid culture (LC) is simply live mycelium suspended in a nutrient solution. It lets you skip the slowest, riskiest part of the growing process — spore germination — and go straight to inoculating grain with active, colonising fungal tissue. Think of it as the difference between planting a seed and transplanting a young plant.

Our Liquid Culture Growth Medium comes as a pre-sterilised, pre-mixed vial. No pressure cooker, no honey-water recipe, no risk of a failed sterilisation batch. You inject a small amount of your spore vial or spore syringe into it, wait for the mycelium to colonise the broth, and then use that colonised LC to inoculate your grain jars, grain bags or all-in-one bags.

What is in the kit?

Everything you need to inoculate the vial hygienically is included. You do not need to buy anything extra for this step.

1× LC medium vial	Pre-sterilised nutrient broth in a sealed vial with a self-healing rubber injection port. Ready to inoculate immediately.
2× alcohol swabs	To disinfect the injection port on the vial and — later — the port on your grain jar or bag.
1× sterile needle	For transferring your spore solution into the vial. Also used later to draw colonised LC back out.
1× sterile 10 ml syringe	For drawing up your spore solution and, once colonised, for injecting the LC into grain.

What can you inoculate it with?

Not all spore products work equally well as a starting point. Here is what we recommend and what to avoid as a first step.

Spore vial (recommended)	Our own liquid spore suspension. Ready to draw into the included syringe and inject. Most straightforward option.
Spore syringe	Works exactly the same way as a spore vial. We no longer sell syringes, but if you have one from elsewhere, it is fully compatible.
Clean agar wedge	A small piece of visibly clean mycelium from a colonised agar plate, transferred with a sterile scalpel. This is the cleanest possible input.
Spore swab (advanced only)	Not recommended as a direct input. See the note below.

Using a spore swab? Do not put it directly into the LC vial. Cotton fibres and traces of moisture on the swab increase the risk of contamination in a nutrient-rich liquid. The recommended route is swab → agar plate → clean mycelium wedge → LC. See our Spore Swab guide for the full two-step method.

How much do you inject?

More is not better. A larger inoculation does not colonise faster — it just increases the contamination risk. Match the volume to the size of your medium vial:

LC medium volume	Inject
5 ml vial	0.5–1 ml
10 ml vial (this product)	1–2 ml
50 ml jar	5–10 ml

The included 10 ml syringe is more than enough for the vial itself — you will use the rest of its capacity later to inject the finished LC into grain.

What you need for a clean workspace

The kit is complete for inoculating the vial, but you will also want a few extra hygiene tools. These make the difference between a clean colonisation and a contaminated one:

A butane torch lighter to flame-sterilise the needle — a normal lighter works but is slower and less hot

Surface disinfectant spray for wiping down your work surface, the outside of the vials, and any tools

Opsept hand disinfectant to clean your hands and wrists before you start

Sterile nitrile gloves — one pair, put on right after hand disinfection

A face mask to keep your breath away from the vial and needle

A still-air box or a very clean, draught-free space (kitchen with all doors and windows closed, surfaces just wiped down)

A marker pen and label for the strain name and date

Speed and cleanliness are the two factors that determine success at this stage. Do not open anything until you are ready to use it. Every extra second the vial or needle is exposed to unfiltered air is a chance for contamination to land.

Step-by-step: inoculating your LC vial

1
Prepare your workspace

Close all doors and windows. Spray your work surface, the outside of the LC vial and your spore vial or syringe with surface disinfectant and wipe dry with a clean paper towel. Disinfect your hands and wrists with Opsept, put on your sterile nitrile gloves and your face mask. If you have a still-air box, work inside it and let the air settle for five minutes before starting.

2
Shake your spore source

Shake your spore vial or spore syringe for 30 to 60 seconds. Spores settle at the bottom, and you want them evenly distributed before drawing them up.

3
Draw up 1–2 ml of spore solution

Attach the sterile needle to the sterile 10 ml syringe. Wipe the injection port of your spore vial with one of the included alcohol swabs. Insert the needle through the port and draw up 1 to 2 ml of spore solution. Do not touch anything with the needle tip.

4
Flame-sterilise the needle

Hold the needle in the flame of your butane torch lighter until it glows red. Let it cool in still air for 10 to 15 seconds — do not wipe it, do not touch it to any surface. This kills anything that landed on the needle while you were drawing up spores.

5
Wipe the LC vial injection port

Use the second alcohol swab to wipe the rubber injection port on the LC medium vial. Give it a few seconds to dry.

6
Inject into the LC vial

Push the needle through the injection port at a slight angle. Inject your 1–2 ml of spore solution slowly, aiming toward the side of the vial rather than straight into the liquid. Withdraw the needle slowly to avoid pressure spray.

7
Swirl gently

Give the vial a gentle swirl for 10 to 20 seconds to distribute the spores through the broth. Do not shake violently — that creates foam and forces liquid into places it should not go.

8
Label and store

Label the vial with the strain name and the date. Place it in a dark spot at room temperature — 21–24 °C is ideal. Below 18 °C, germination slows significantly. Direct sunlight and hot spots (near heaters, on top of routers) are out.

Incubation — what to expect

Growth is slow at the start, then accelerates once the spores germinate. Do not panic if you see nothing for the first three days.

Day 3–7	First tiny wisps of white mycelium appear, often near the bottom or clinging to the side of the vial.
Day 7–10	Visible white strands spreading through the broth. The liquid should still look clear to light amber.
Day 10–14	The LC is fully colonised: white, stringy mycelium clouds throughout the vial. Ready to use.

Swirl once a day. A daily gentle swirl breaks up surface growth, spreads the mycelium through the broth, and mixes in fresh oxygen. Healthy LC turns increasingly stringy and white rather than uniformly opaque.

Healthy vs contaminated LC

Before you use your LC to inoculate anything, look at it carefully. This one check saves entire grain batches.

Healthy LC looks like this

White to cream-coloured, stringy mycelium strands

Clear to light amber liquid around the mycelium

No smell, or a very faint earthy/beer-like note

Some mycelium may clump at the bottom in a still jar — that is normal

Discard immediately if you see

Green, black, pink, orange or yellow patches — these signal Trichoderma or other mould

Uniformly milky, cloudy liquid — bacterial contamination

Any sour, foul, cheese-like or rotten smell

A film or skin on the surface with off-colouring

Never inoculate grain with a contaminated culture. If you see any of the signs above, seal the vial and dispose of it. A single contaminated grain jar can spread mould through your entire workspace.

Test on agar first (optional but strongly recommended)

Even if your LC looks perfect, a bacterial contaminant can be invisible in liquid. The safest way to confirm your LC is clean is to streak a drop onto an agar plate and watch it for 3 to 5 days. If only white mycelium grows, your LC is clean. Anything else — coloured colonies, slime, unusual smells — means you should not use it on grain.

To make agar plates you can combine our Agar Agar powder with Light Malt Extract (LME) — the classic MEA recipe — and pour into petri dishes. Seal with Parafilm to keep contaminants out during incubation.

Step-by-step: using your LC on grain or substrate

Once your LC is fully colonised and confirmed clean, it is ready to inoculate grain bags, grain jars or all-in-one bags.

1
Bring the LC to room temperature

If you stored the LC in the fridge, take it out at least 30 minutes before use. Cold LC shocks the mycelium and slows colonisation.

2
Shake gently to redistribute mycelium

Give the vial a gentle swirl for 10 to 20 seconds. You want the mycelium spread through the broth, not clumped at the bottom.

3
Flame-sterilise the needle

Same as before: needle glowing red in the flame of your torch lighter, cool for 10 to 15 seconds. Do this between every jar or bag if you are inoculating more than one — one contaminated container should never contaminate the next.

4
Draw up your LC

Spray the LC vial's injection port with surface disinfectant or use an alcohol swab. Insert the needle, tilt the vial to get the liquid onto the port side, and draw up your dose. If the needle clogs on a piece of mycelium, gently push a tiny amount back in and try again.

5
Inject into your grain container

Wipe the grain jar's or bag's self-healing injection port with disinfectant. Insert the needle and inject 1–3 ml per quart jar, 3–5 ml per grain bag, or 2.5–5 ml per all-in-one bag. Aim toward the side of the container so the LC runs along the glass or plastic rather than pooling in one spot in the grain.

6
Label and incubate

Label with strain and date. Incubate at 21–24 °C in the dark. Because the mycelium is already active, grain jars inoculated with LC colonise dramatically faster than those inoculated with spores — often visible growth within 5 to 7 days and full colonisation in 2 to 4 weeks.

Inject at 2 to 4 points around a grain jar. Multiple inoculation points give you multiple starting colonies, and full colonisation completes days faster than a single-point inoculation.

Storing your LC

A fully colonised vial keeps for months if you store it correctly.

Fully colonised LC: store in the fridge at 2–8 °C. Shelf life up to 6 months.

Un-inoculated LC medium vial: store cool and dry, away from direct sunlight. Shelf life up to the date printed on the packaging.

Before using refrigerated LC, take it out at least 30 minutes before inoculation to warm to room temperature.

If you see mycelium growth stall completely in the fridge, that is normal — it wakes up again once warm.

Common mistakes to avoid

Injecting too much. A richer solution encourages bacterial growth more than it speeds up mycelium. More is not better.

Skipping the needle flame. Between jars, always re-flame. This is the single biggest cause of contamination when inoculating multiple containers.

Never swirling. Without daily agitation, mycelium colonises only the surface and starves the rest of the vial.

Using cold LC straight from the fridge. Shocks the mycelium and slows colonisation.

Injecting a spore swab directly. Cotton fibres and residual moisture make this the highest-risk input. Go via agar instead.

Using LC that looks or smells off. If in doubt, throw it out.

Choosing the right spore format

Liquid culture medium is one part of a bigger picture. Here is where each spore product fits:

Spore vial	Liquid spore suspension. The ideal starting point for the LC medium in this guide. Also directly usable for grain inoculation.
Spore swab	Best for agar work and microscopy. Not a direct LC input — go via agar first.
Spore print	Long-term archive format. Most cost-efficient per strain. Requires scraping into a sterile liquid to use.
Liquid culture (this product, once colonised)	Active mycelium — not spores. Fastest colonisation, lowest contamination risk on grain. Ready to inoculate substrate directly.

Browse our full spore and liquid culture collection.