Liquid culture in the context of mushroom cultivation refers to a specialized growth medium used to propagate mycelium, the vegetative part of mushrooms, in a liquid form. This technique is commonly employed by mushroom enthusiasts and commercial growers to efficiently expand mycelium cultures before inoculating substrates for mushroom production. Here's how to create a liquid culture medium for mushroom cultivation:
Materials Needed:
- 15 grams light malt extract
- 2 gram brewers yeast
- 1 liter water
- Quart mason jar
- Modified lids for mason jar with injection port
- Pressure cooker
- Aluminum foil
- Kitchen scale
- Mycelium grown on agar plate or liquid culture
- Magnetic stir bar
- Magnetic stirrer
Procedure:
Step 1: Measure Ingredients
To achieve precise measurements, utilize a digital kitchen scale to weigh the light malt extract and brewers yeast.
- 15g light malt extract
- 2g brewers yeast
Measure out 1 liter (1000 ml) of water.
Step 2: Mix Ingredients
Add the malt extract and brewers yeast to the mason jar then add the water. During this time, add the magnetic stir bar to the mason jar. Mix well to dissolve the malt extract and yeast.
Step 3: Prepare the Mason Jar for Pressure Cooker
Place lids on the jars but do not close them tightly; you should allow for some ventilation. The lid should be able to turn very easily. Wrap the top of the lid and mason jar with aluminum foil for an added layer of protection.
Refer to picture below for example of modified mason jar lid with injection port and air exchange filter.
Step 4: Sterilize the Medium in Pressure Cooker
Lay a rack at the base of your pressure cooker to serve as a protective barrier, safeguarding the jars from direct exposure to the heat source.
Sterilize the jars and contents in a pressure cooker at 15 psi for 40 minutes. Once the contents have finished sterilizing in the pressure cooker, allow it to cool down to room temperature. Avoid opening the jar or pressure cooker while it is cooling to maintain sterility and safety.
Step 5: Inoculate the Medium
Liquid Culture
If you're working with a liquid culture syringe, ensure you evenly disperse the mycelium by giving it a thorough shake.
Use a torch or an alcohol lamp to heat the needle of your syringe until it glows red hot to eliminate any potential contaminants. Allow the needle to cool before proceeding.
Insert the needle through the self-healing injection port of your mason jar lid and gently depress the plunger, introducing approximately 1-2ml of the liquid culture into your liquid culture medium.
Agar Plate
When using mycelium grown on agar, prepare a small piece using a sterilized scalpel.
Use a torch or an alcohol lamp to heat the blade of your scalpel until it glows red. Allow the scalpel to cool before proceeding.
Slightly open the mason jar lid to insert the agar piece swiftly and then promptly reseal it. We recommend doing this step in front of a flowhood or a still air box to minimize the chance of contamination.
After inoculating your liquid culture medium, gently shake the jar to evenly disperse the mycelium throughout the liquid.
Place your jar in a dark location at room temperature and allow it to incubate.
We highly recommend growing out mycelium on agar plates before adding to liquid culture media just in case the liquid culture you have is contaminated.
Step 6: Agitate
Once your inoculated liquid culture begins to exhibit signs of mycelium growth, it's crucial to regularly agitate the mixture. Agitation serves the purpose of disintegrating the developing mycelial mass and ensuring an even dispersion within the liquid medium. This practice enhances nutrient consumption efficiency and results in a more easily syringeable liquid culture for substrate inoculation.
Position the jar on the stirrer and set it to a moderate speed. This generates a vortex in the liquid, effectively disassembling the mycelial mass and distributing it evenly.
Repeat this process at least once a day until you're prepared to utilize your liquid culture. Consistent agitation is essential for preserving an even distribution of mycelium throughout the liquid culture, supporting robust and healthy growth.
