Liquid culture or LC as it’s often referred too is mycelium suspended in a nutrient broth. The purpose of LC is to make inoculating substrates and grain spawn easier. The risk of contamination is lower because the culture goes from a sterile environment (Inside the jar) to the sterile syringe and is injected into the new, sterile environment rather than transferring with agar wedges, increasing the risk of contamination, especially to more inexperienced growers.
LC does have some downsides, because it doesn’t grow on a ‘horizontal plane’ like agar does, contamination can hide in and amongst the suspension, only showing itself once the culture is dropped into a new environment, this is why working as clean as possible with your culture and LC is very important.
Once you have a bottle of sterilised ‘broth’ you drop a sample of your desired culture into it. Within 7 – 14 days you’ll see the mycelium has ‘clouded’ the culture and expanded throughout; this is aided with semi-regular mixing/shaking. This can be achieved by use of a magnetic stirrer, a bolt in the bottom or just swirling by hand.
Things you’ll need:
AirPort Jar – Here is my guide on how to make them.
Syringes – Around 10ml will be enough to do 10 jars+
Needles – The bigger the number the smaller the needle will be. I suggest 18 gauge and as long as you can get them.
Firstly, dissolve 20g of LME into 1 litre of water, I tend to this with hot/boiling water as it helps dissolve it better.
Fill your jars/jar approximately 80% full with broth.
If you have a magnetic stirrer add it now, if not, add a bolt. If you don’t have a bolt, don’t worry you’ll just have to swirl a bit more. Place your broth into the PC and cook for 15 minutes at 15psi. Cover the tops in tin foil to protect the filter.
Wait for the PC to naturally vent pressure. Forcing the PC to a lower pressure by removing the rocker or opening the valve will cause your broth to overboil and push up through your filter, making a right mess. Once the PC is at zero, remove the jar and wait for your broth to reach room temperature, anything too high will stunt/kill the culture so be patient.
Prepare your area under the sterile working condition of your choice i.e. SAB or Flowhood, all surfaces rubbed down with 70% Isopropyl Alcohol including the jar, flame lamp for the scalpel etc…
Transfer a small wedge, roughly the size of a 1st class stamp to your jar.
Seal each jar TIGHT and add some micropore tape/parafilm around it for good measure.
Incubate at the appropriate temperature for your species, I’m using blue oyster so I will incubate at about 24c. Wait 7 – 14 days to allow for colonisation, once you begin to see growth, give the jar a gentle swirl/stir and repeat as needed to break up the structures and ensure the whole broth is colonised.
This step is optional, stir/swirl your culture and take a sample by drawing it into a sterile syringe with a heat-treated needle through the injection port and dropping a single drop onto agar and allow the mycelium time to colonise
If your sample is clear and it colonises normally without contamination, continue using it in the knowledge your LC is clean and ready to use!