Liquid culture is a great way to start growing mushrooms from spores. They take a lot of the guess work out of the process by allowing you to see that the spores have successfully grown and started fusing to make mycelium before you transfer into grain to make spawn. The process for making and starting a liquid culture is very simple, but requires good aseptic technique as it is very easy to contaminate. Let’s dive right in!

Step 1: making liquid culture medium for mushrooms

Liquid culture for fungi spores is dead simple. There’s no complex ingredients or nutrition requirements for most commonly grown species. The ingredients you need are sterile water and light malt extract.

That’s it.

The solution should be prepared in a 1:5 ratio light malt extract to water. This means if you have 5ml of water you will 1g of light malt extract, for 750ml of water you’d add 50g light malt extract, and so on.

While the solution is easy to make, it needs to be stirred well and also sterilized carefully. The sugars in the liquid solution can easily caramelize if you heat them too quickly or at too high of a heat. Use a raised platform in your pressure cooker to keep the container off the bottom so it heats more evenly.

Sterilize your liquid growth medium at 15psi for 45 – 90 minutes. Be sure to place foil over the lid of your container to maintain sterile transfer.

Step 2: Adding spores or Mycelium

You can add spores directly to your liquid culture once it has cooled to room temperature. Alternatively you can add mycelium you’ve grown on agar, however this might leave clumps in your liquid if you do not mix the solution well enough. For liquid additions of a spore syringe or liquid culture you don’t need to add more than 2-4ml per pint, but a safe bet is to add 1ml of spore suspension for every 100ml of liquid culture you are inoculating.

When adding either spores from a spore syringe or a agar sample, you need to be extra careful not to contaminate your liquid culture. It may be simple, but it is the perfect growth medium for fungi of all types and can easily become contaminated. Be sure to work in a glovebox or flow hood and take every precaution to avoid exposing unclean air to your liquid medium.

Once your culture is inoculated with spores or mycelium, wait one to two weeks for it to colonize in a sealed container with a filter vent. The culture will grow at room temperature, but most mycelium favors slightly elevated temperatures. After this you can draw up the liquid culture into sterile syringes working in a sterile environment. The syringes are then ready for use and will keep 6 months to a year if stored in a refrigerator (not frozen!)

Liquid Cultures are Easy and Accessible

Liquid culture preparation is another core skill of the average mushroom cultivator. Once you get this down you’ll be well on your way to running your own fungiculture operation from start to finish. Next up learn how to make grain spawn using the liquid culture you just created!