Light malt extract is the perfect ingredient for making liquid culture for mushrooms due to its nutritional profile and clear appearance once mixed and sterilized.
LME liquid culture will allow you to get a better view of how the mycelium is growing in the jar whilst allowing you to identify contamination early on the culture's expansion.
Alongside this the recipe is grain-based which means the mycelium growing inside the culture is already breaking down the starches and nutrients commonly found in grains.
This means later when you inoculate a grain jar with the liquid culture the mycelium already understands how to break down some the nutrients in the grains, resulting in faster colonization.
Light Malt Extract Liquid Culture Recipe.
Typically for Light Malt Extract Liquid culture I use 1g Light Malt Extract to 600ml of water. This will produce a clear liquid culture in which the mycelium will flourish.
Below is a calculator which can be used to calculate your own mix based on this ratio.
LME Liquid Culture Calculator.
How do you make liquid culture with light malt extract (LME)?
Mason Jars (or any other glass jar such as a recycled sauce jar).
Digital Scale – You will want to get some scales which can measure to decimal places.
Tin Foil and Rubber Band.
Micro-pore tape/polyfill/Gas exchange lids (here is a discussion on gas exchange lids, however for this tutorial micropore tape will do).
Stir Bar (optional).
To create Liquid Malt Extract (LME) culture you do the following:
Step 1 – Create Lids.
If you don't have gas exchange lids like this, then put a small hole (about the size of a nail) in the top of the lid, as close to the glass as possible (this makes it easier to extract your culture). Then cover it with 2 layers of micropore tape. Alternatively you can purchase pre-made lids such as this.
Step 2 – Weight Out LME.
Using a digital scale, I weigh out the desired amount of liquid malt extract. I weigh out 1g of LME and then place it into the jar. I then give it a bit of a stir to spread out all the powder.
Step 3 – Fill Jar With Water.
Next I fill the jar with the desired amount of liquid, I will be using 600ml of water. Shake and mix the jars so all the LME has dissolved. Then add a stir bar into the mixture if you are using one.
Step 4 – Secure The Lids.
I place the lids on the jar and secure. Next, I cover the lid with tin foil and then secure the tin foil with an elastic band as shown here.
Step 5 – Sterilize Jars
Put the jar into your pressure cooker and add 2 quarts of water (or up to the minimum line on your own pressure cooker). Sterilize at 15psi for 15 minutes.
Note: Some people like to sterilize LC at a lower heat for a longer time (around 25 minutes) as it helps them get a clearer culture.
Step 6 – Wait
Once the timer is complete I turn off the heat and allow the pressure cooker to cool slowly over a few hours.
Note: It is important to allow the pressure cooker to cool for a few hours before opening the lid of the pressure cooker, if you don't you risk contaminated air being sucked into the jars because of the temperature.
Here we are going to discuss inoculation using the Light Malt Extract Liquid culture.
It is recommended to use a still air box or flow hood when performing these steps.
However, I have had plenty of success working clean and fast on a kitchen counter so don't worry if you don't have these.
I will be using my miniature laminar flow hood in this tutorial. This isn't perfect it has a 99.95% filtering effect which is probably questionable and not comparable to a commercial setup. However i've had plenty of success knocking up grain spawn jars, liquid culture and agar at home using this and its easier to setup than my still air box.
Butane Torch (seriously get one of these it makes flame sterilizing needles very very easy, and the needle will glow red in seconds).
Liquid Culture Syringe.
First I clean down the surfaces which I will be doing my inoculation using rubbing alcohol.
Next, I remove the LME jar from the pressure cooker and place all my liquid culture syringe and micropore tape on the cleaned surfaces.
I remove the foil and wipe the tops of the lids down with alcohol. Then wipe down any of my utensils with alcohol too.
Next, I place a small piece of micro-pore tape on the lid and fold it back. This tape should be long enough to cover the hole you are going inject your mycelium through.
Note: If you are using jar lids like this you dont need to worry about this step.
Next flame sterilize your needle using the butane lighter until it is glowing red.
Quickly insert the syringe into the hole and tilt the jar so the needle is submerged in water and has a few seconds to cool down.
Next, push down on the plunger injecting about 1ml of liquid culture into the ligh malt extract liquid culture.
Finally remove the syringe from the jar and quickly flip down the micropore tape which you had set on the side.
Place you jars somewhere cool and dark then wait.