Liquid cultures are more popular than ever among mushroom growers. This is due to the fact that using them is both practical and safe. In this article, we discuss the pros and cons of liquid cultures and explain step by step how to best use a liquid culture syringe.
Table of Contents
What is liquid culture?
When we talk about liquid culture, we mean a fungal culture that grows in a liquid. This liquid is carefully composed and contains sugars, so the fungus can live and grow in it. A commonly used ingredient for the sugar solution is honey, because it’s cheap and easy to find. In addition to the base ingredient, other ingredients can be added to further promote the growth of the fungus.
After mixing, the liquid needs to be sterilized to make sure there are no living microorganisms left. This way, the fungus can grow undisturbed in the sugar solution without contamination from bacteria or other fungi.
Inoculating liquid culture
After the liquid is sterilized, fungus needs to be added. This process is called inoculation. A liquid culture can be inoculated in different ways.
The simplest and fastest method is to directly add mushroom spores to the sterile sugar solution. However, this is also the least safe method, since there’s a significant chance the spores are contaminated. Because contamination in a liquid culture is hard to detect, this can be problematic.
Another method involves first culturing mycelium on an agar medium. This method is much safer, because it’s relatively easy to see on agar whether the mycelium is contamination-free. If that’s the case, a small amount of mycelium is added to the sterile sugar solution, after which the mycelium is further grown.
A big advantage of this method is that it allows you to create liquid cultures from selected genetics. Proven and tested genetics usually lead to more consistent results in mushroom cultivation.
What are the pros and cons of liquid culture?
Liquid cultures have a range of pros and cons. Below is a brief overview so you can weigh the options at a glance.
| Pros | Cons |
|---|---|
| ✅ Rapid colonization thanks to multiple inoculation points | ❌ More susceptible to contamination and more difficult to diagnose |
| ✅ Inexpensive to make | ❌ Unsuitable for the selection of genetics |
| ✅ Relatively long shelf life if refrigerated |
How do you inoculate mushroom spawn with a liquid culture syringe?
Inoculating mushroom spawn with liquid culture isn’t difficult, but there are a few things to keep in mind. You’ll need various materials and tools, and it’s important to work in a clean environment and in a hygienic way. Read on to learn more.
Supplies
Essential
- Liquid culture syringe
- Sterilized grains in a jar or bag with micron filter(s) and injection port
- Lighter or gas burner
- Face mask
- Nitrile gloves
- Disinfectant
- Alcohol wipe(s)
Optional
- Flow hood
- Still air box (SAB)
Steps
Before you start inoculating, it’s important to choose a suitable workspace. Preferably choose a compact area with minimal airflow, as this is easier to disinfect. Once you’ve found and prepared a suitable workspace, follow the steps below.
1. Disinfect your hands
Start by putting on nitrile gloves. Disinfect them with an appropriate disinfectant or 70% isopropyl alcohol and let them air dry.
2. Disinfect the injection port
Take an alcohol wipe and disinfect the injection port(s) of your spawn jars or bags. For extra safety, you can leave the alcohol wipe on the injection port until you’re ready to inoculate.
3. Remove the needle cap
Grab the liquid culture syringe and shake it well to loosen up the mycelium. Then attach the needle to the syringe. Do these steps as quickly as possible to avoid contamination.
Finally, remove the protective cap from the needle.
4. Heat the needle
Heat the needle with a lighter or gas burner to kill any microorganisms that may have settled on the needle in the meantime.
Be careful when using a gas burner, as plastic parts of the needle can melt if overheated.
5. Insert the needle into the injection port
Let the needle cool for a few seconds after heating to avoid damaging the injection port. Then remove the alcohol wipes from the injection port(s) and insert the needle.
6. Inject the liquid culture
Inject about 5 ml of liquid culture per 650 ml of grains. Preferably do this with a light twisting motion. This spreads the mycelium evenly over the sterile grains, which usually results in faster colonization of the substrate.
My substrate is inoculated, now what?
Once all containers, jars, or bags are inoculated, it’s time for the incubation phase. Move the containers to a warm space with as stable a temperature as possible. By creating optimal growth conditions, the fungus will colonize the substrate quickly. For more info, check out our article on incubating mushroom spawn.