How To Make Liquid Culture For Mushroom Cultivation.

Liquid culture (also known as liquid broth culture or LC) is a sterilized nutritious solution which can be used as a media to grow, store and swap mycelium tissue while growing mushrooms. 

There are several liquid culture recipes to choose from which I will discuss in this guide.

Learning how to make liquid culture is a great skill for people wanting to grow mushrooms for mycology.

It is often the stepping stone for beginner growers who don’t have the sterile technique to perform agar work.

Mushroom growers can create unlimited liquid culture spawn from one LC syringe and use it to inoculate grain jars, and, because liquid culture lasts for months it is perfect for home growers.

By the end of this post you should know how to make at least 3 liquid culture recipes for growing mushrooms and understand what bad liquid culture looks like. 

Once you've read this checkout how to use liquid culture to learn techniques on using LC.

How To Make Liquid Culture?

Liquid Culture Broth is created by adding a nutritious medium into water and sterilising the mix.

For mushroom growing the culture is often enriched with sugars to feed the growing mycelium. 

I have created a table below which covers the most common liquid culture recipes, choose a mixture you wish to use then follow the instructions in this post. 

Recipe Name	Nutrient Amount (Grams)	Water	Percentage (NA:W)
Karo LC	24g	600ml	4%
Honey LC	24g	600ml	4%
LME LC	1g	600ml	0.16667%

 

If you want to create a formula which is not listed in this table then you simply do the following:

(Water X Percentage) / 100 = Nutrient Amount.

OR

(Nutrient Amount / Percentage) X 100 = Water.

OR
Follow the links in the table which contain a more detailed table for each tek.

Step By Step Guide To Create Liquid Culture

These techniques discussed require you to have and use a pressure cooker, if you don't have one checkout my post about the best pressure cooker for growing mushrooms at home.

We recommend creating multiple jars at one time to improve the chances of creating a clean liquid culture broth.

Requirements

• • Pressure Cooker (pressure cookers for mushroom cultivation).
  • Micro-pore tape/polyfill (here is a discussion on gas exchange lids, however for this tutorial micropore tape will do).
  • Liquid Culture Syringe
  • Nutrient (Honey, LME, Karo).
  • Butane Torch (seriously get one of these it makes flame sterilizing needles very very easy, the needle will glow red in seconds).
  • Jars
  • Alcohol
  • Stirring plate (this will speed up the process).

Step 1 – Create Mixture.

Find a glass jar and put a hole in the lid using a screwdriver or something similar.

The hole should be as close to the edge of the lids as possible as show in this picture below.

Next, fill the jar with with 600ml of warm water. It is better to use distilled water but realistically tap water will also work fine.

Measure out the amount the amount of nutrient you are going to be using and add it to the jar then give it a quick swirl/mix with a spoon.

Place 2 strips of micropore tape over the hole you created in the lid and screw on the lid to the jar.

Finally, place some foil over the top of the jar and secure it with a rubber.

Step 2 – Sterilize Jars.

Place the liquid culture jar into your pressure cooker and heat until the pressure reaches 15psi.

Once 15psi is reached leave for 30-40mins to sterilize the culture.

When the time is up, turn off the heat and allow the pressure cooker to cool overnight before moving to the next step.

Step 3 – Inoculate Liquid Culture Mixture

The first thing you want to do is find somewhere to inoculate your mixture. It is possible to do this on a kitchen counter if it is clean however using a still air box is always advised.

• Collect your butane lighter, liquid culture syringe and micro-pore tape.
• Wipe down your surfaces and put on gloves and a face mask.
• Remove the jars from the pressure cooker.
• Wipe the lid of the jar with alcohol wipes.
• Pop a piece fo micro-pore tape on top of the jar which you are going to fold down.
• Shake the needle to spread out the current mycelium.
• Flame sterilize the needle until it is glowing red.
• Insert syringe and inject 1cc of liquid culture.
• Remove the syringe and flip down the micropore tape.
• Place the jar into incubation temperatures(18-20c or 64-68f).

Step 4 – Wait.

• Stir the jar daily to prevent clumpy solid mycelium masses (without opening the jar).

Note: Alternatively you can place your jar onto a stirring plate to speed up the process.

What Does Good/Bad Liquid Culture Look Like?

An example of both good and bad culture can be found at the end of the YouTube video I have create below on this very topic.

Good Culture

The liquid should be clear and you should be able to see through to the other side of the jar. Inside the liquid, there should be a white clump of mycelium or lots of little clumps.

Bad Culture

Common signs of contamination are if the culture is cloudy and you cannot see through it  (wait a week after inoculation to check this as sometimes the mycelium cleans up the culture), if it releases a foul smell or has a green colour scum on the top of the culture when it is left to settle for a few days.

Normally the best way to find out if the culture is clean is to try it out on grain or agar and see if it contaminates. If you follow sterile technique but the jars are repeatedly being contaminated in the same way it’s likely your jar of liquid culture. 

Why Make Liquid Culture?

• Faster Growth – Since the medium already contains live mycelium it normally colonises a substrate substantially faster. This gives LC an advantage over spores.
• Unlimited Mycelium Supply – if you learn how to make liquid culture you can turn 1 LC syringe into an unlimited supply. However, you must take senescence into consideration (so use a master jar).
• It’s Cheap – making liquid cultures is very cheap and can be done with household ingredients.

Does Liquid Culture Need Gas Exchange?

No, Liquid culture does not need gas exchange. The mycelium is submerged in a liquid solution therefore there is no need to for air exchange holes to be placed in your lid.

I am not sure exactly how the mycelium breaths in this situation however it most likely has something to do with absorbing the oxygen which makes up H2O (water).

Does Making A Liquid Culture Require A Pressure Cooker?

Actually, no, you can sterilize the  liquid culture recipe in a microwave if you don’t have a pressure cooker.

Place your mixture into a microwavable container, the put it inside the microwave for 3 minutes, remove and shake, then place it in for another 3 minutes.

How Long Does Liquid Culture Last?

Liquid Culture can survive at room temperature for 6 months until the nutrients in the solution have been used up.

So you're Liquid culture is good for a decent amount of time suspended in the solution

If you need to your liquid culture to last longer putting it into a refrigerator should allow it to survive for years. 

When to Stir/Shake Liquid Culture?

It is recommended to shake or stir (using a magnetic stirrer like this) at least once a day. 

If you don't do this the mycelium will create a huge blobby mass as seen below. 

This also speeds up the expanding process as there is more surface area for the mycelium to grow off.

I did not shake those Jars so I could highlight what a clean culture would look like (clear).

How Long Does Colonization Take?

Liquid culture usually takes between 7-14 days to accumulate enough mass to be used in an actual inoculation.

It can take longer for the Jar to be completely colonized and the growth to slow down.

Several factors can come into play here such as whether you shake the culture, temperature and Mycelium vigour.