Liquid culture is an elegant solution for rapid mycelium transfer and offers benefits that many growers appreciate. The mycelium grows in a nutrient solution and can be easily measured and distributed—which is particularly advantageous for larger projects. To ensure the mycelium colonizes the entire liquid evenly, the culture is agitated regularly (shaking or using a magnetic stirrer fragments the mycelium), allowing new growth points to form throughout.
The Recipe
Production begins with a proven recipe. The simplest options are honey water (about 2–3% honey in distilled water) or a light malt extract solution (liquid MEA – Malt Extract Agar without agar). A good rule of thumb is a nutrient density of about 2–4% malt extract, which corresponds to roughly 20–40 g of malt extract per liter—for four liters of liquid culture, that would be about 80–160 g. Optionally, you can add a little yeast extract depending on your desired nutrient density. Fill the solution with distilled water and stir thoroughly.
Sterilization
Sterilization is also necessary here. Fill the solution into small bottles or jars with wide openings. Important: When sterilizing in a pressure cooker or autoclave, the container must never be completely airtight—otherwise, excess pressure will build up and create a risk of bursting. Therefore, place the lid on loosely or use a self-healing injection port or a microfilter that allows for pressure equalization while keeping growth sterile later on. Sterilize at 15 PSI for about 20–30 minutes. Caution: Liquid culture can splash during sterilization—so use sturdy containers and do not fill them to the brim.
Inoculation
After cooling, the liquid culture is inoculated. Preferably inoculate using a pure agar or mycelium culture—a few mycelium fragments are sufficient. While inoculating with a spore syringe is possible, it is considered significantly more prone to contamination and leads to inconsistent multi-strain cultures; for a clean, uniform liquid culture, a pure mycelium culture is the better choice. Inoculation should take place under aseptic conditions—work in a Still Air Box (SAB) or at a Laminar Flow Hood. Very small quantities can also be handled with low risk of contamination using flame sterilization (briefly heating the tool over a Bunsen flame).
Distinguishing healthy from contaminated culture
Healthy mycelium appears white or creamy and spreads evenly throughout the solution. The liquid remains clear or slightly milky. Within 5–14 days, you should observe visible growth—threads growing from the mycelium inoculum or a fine turbidity. Contaminations, on the other hand, appear as discolorations (green, black, orange), unpleasant odors, or streaky, oily surfaces.
⚠️ In case of contamination: do not open, do not use. Never open or reuse a contaminated or moldy bottle. Mold (e.g., green or black species) can release harmful spores—do not inhale spores and do not stir them up. Dispose of the container while closed.
Storage
Storage is simple: Proven liquid culture can be stored at room temperature for several months—ideally in the dark. It is even better in the refrigerator (4–10 °C), where the culture remains viable for two to four months or longer. Shake the bottle thoroughly before use so that the mycelium is evenly distributed.
⚠️ Safety instruction – Fungal spores (respiratory tract)
Mature mushrooms release spores. Inhaling large quantities of spores can irritate the airways and lungs and, with repeated exposure, trigger allergic reactions or even hypersensitivity pneumonitis ("Mushroom Worker's Lung").
- Allow mushrooms to fruit in well-ventilated rooms; do not place them in bedrooms or living areas.
- Harvest mushrooms just before they release their spores to reduce spore load.
- Sensitive, allergic, or pre-existing individuals, as well as those with chronic exposure: wear respiratory protection (FFP2/FFP3).
- Never consume contaminated or moldy cultures; dispose of the bag closed and avoid stirring up/inhaling spores in the process.