Urban Spore

How To Make Liquid Culture

Liquid culture syringe

What Is Liquid Culture?

Liquid culture is used as a starter culture for mushroom cultivation. It is used to either inoculate agar plates, sterilised grain for spawn production or to expand and create more liquid culture.

Liquid culture is often produced in jars with modified lids from a sterilised broth containing a specific ratio of sugar to water. This broth is inoculated with a mycelium culture. The mycelium will consume the sugar and continue to expand producing near infinite quantities of mycelium.

Liquid culture is extracted from the jar with a syringe via the injection port in the modified lid. The needle point of the syringe can be heat sterilised to prevent the transfer of contaminants.

liquid culture

How To Use Liquid Culture

Liquid culture can be used to produce grain spawn by inoculating sterilised grain .Using aseptic technique as little as 2 cc of well colonised liquid culture can be administered to the sterilised grains. The mycelium will feed on the grains as it colonises over the following 2 – 4 weeks.

growing king oyster mushrooms on hardwood

Preparing Jars For Liquid Culture

Liquid culture requires fresh air exchange for healthy development. As mycelium grows it releases carbon dioxide. In order to introduce more oxygen we must create modified lids. 

Each modified lid will feature a filter for fresh air exchange and injection port to allow for a syringe to inject & extract material without introducing contamination.

Alternatively, modified lids can be purchased here.

Learn more about making liquid culture jars in our step by step guide by following the link below.

What You'll Need

The recipe for making a liquid culture broth is very simple. It requires a sugar concentration of 4%. A number of different sugars or starches can be used. We prefer light malt extract as powders are easy to measure. Karo or corn syrup will produce a clear but slightly slower growing liquid culture.

Brewers yeast is an optional additive for faster growing mycelium. 

Buy Modified Mason Jar Lids

Modified mason jar lids make the production of mushroom grain spawn and liquid culture a breeze.

Each lid features a filter patch for fresh air exchange and reusable injection ports for easy inoculation with a liquid culture syringe.

Step 1. Measure Ingredients

Using precision scales measure the light malt extract and brewers yeast (optional).

Step 2. Bottle & Cover

Half fill each mason jar with liquid culture broth. 

Add a piece of glass marble or a magnetic stir rod. This will assist in breaking up clumps of mycelium later on. 

Place modified lid on each mason jar and cover with a piece of aluminium foil.

modified lids for mushroom growing

Step 3. Sterilise

Using a pressure canner sterilise the liquid culture broth for 20 minutes at 15PSI. 

Allow the pressure canner to cool completely before opening.

Choosing A Pressure Canner

The Presto 23 Quart Pressure Canner is an excellent option for sterilising media for mushroom growing.
It has capacity for sterilising up to 24 x half-pint mason jars.

Note: Using pressure canners for mushroom growing may void the warranty.

Step 4. Inoculate

The cooled sterile sugar broth can now be inoculated with a live mycelium culture. It’s important to consider aseptic technique when inoculating with liquid culture. A liquid culture syringe can be flame sterilised &  injected via the injection port. 

Mycelium grown on agar can be added by removing the lid only with the assistance of a laminar flow hood.

Step 5. Agitate

Gently swirl the liquid culture jar daily to increase oxygenation. Take care not to splash liquid near the lid or unwanted pathogens may penetrate. 

For best results the liquid culture can be stirred using a magnetic stirrer.

Magnetic Stirrers & Better Liquid Culture

Using a magnetic stirrer allows for a better, more thorough oxygenation of the liquid culture which will encourage faster & stronger growth. The spinning action of the magnetic stirrer breaks apart the mycelium into small fragments to increase overall inoculation points for the best possible results.

Step 6. Wait

Within 14 – 21 days a large amount of mycelium will have grown in the liquid culture. This can now be used to inoculate more liquid culture, agar plates or even grain spawn.

It’s recommended to test liquid culture on a small batch or agar plate to verify that there are no discreet contaminant piggybacking in the solution.

Liquid culture syringe

Liquid Culture Collection

Liquid culture is a powerful tool in the mushroom growers arsenal. Just a few drops is enough to start the transformation from sterilised grain to vigorous mushroom grain spawn. Liquid culture can be used to inoculate agar plates, grain spawn or even create an endless supply of liquid culture.

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