For a long time now, I've recommended prospective mushroom growers to inoculate their grain jars with liquid culture (LC) syringes because it's so easy. Inject and go! But as I've sourced my liquid cultures from different manufacturers, I've realized that this recommendation can only take you so far before you deal with confusion, disappointment, and contamination.
This is because many liquid culture producers out there have perfectly viable liquid cultures with a hint of contaminants in them. I've found several times from a recent producer I've purchased from that my LC-inoculated grain jars look great, but once I mix it in substrates like coco coir and oak/soyhull bags, they soon become contaminated.
I've provided tried-and-true instructions on completely sterilizing oak/soyhull substrates. So why should they contaminate after mixing with these apparently clean-looking grain jars?
This is because bacteria in the liquid culture can still live with the propagated mycelial culture in a grain jar, just waiting for the opportunity to grow when introduced to the right environment. Trichoderma, the most common bacterial contaminant, grows in oxygen-rich environments; grain jars are not great oxygen environments, and a stronger mushroom culture can crowd out the bacterial contaminant, which lies dormant until it's mixed in the more nutritious, open environment of a bulk substrate like coco coir and Master's Mix (oak/soyhull pellet mix).
In the end, to better guarantee a clean colonized grain jar and a subsequently contamination-free fruiting substrate, you need to isolate the mushroom culture from bacteria through the use of agar in petri dishes. Agar throws a wrench in the easy process I've outlined for growing mushrooms, but it's effective in identifying contaminants and getting rid of them.
This fact has been ignored by me, as I successfully use North Spore's Lion's Mane liquid cultures without any issue, and propagate by own liquid cultures without contamination (you can check out North Spore's liquid culture collection here: https://northspore.sjv.io/Y9zZrB). But for those purchasing from other sources, you'll likely need to propagate the liquid culture in agar to clean out bacteria before inoculating your grain jars. I'll be emphasizing the use of agar in mushroom cultivation over the next few months because I want to make sure future cultivators are equipped with all the knowledge and tools to grow mushrooms without so much contamination. Contamination will happen sometime, but you'll feel much better about it when you've isolated all the variables that come with a liquid culture.
So, bear with me as I develop an easy method of using agar plates to clean up mushroom cultures, and help develop even faster-growing cultures by isolating your best mushroom's strongest traits!