Two years ago I started growing some species of mushrooms on logs and at the moment I have oysters, pholiota nameko and hericum erinaceus fruiting and cloned some for inoculation in next spring
I have worked out a nice and simple sterile technique which works fine for me and can be done in every kitchen with only a pressure cooker
you need:
-pressure cooker
-some screw cap jars
-substrate (I use 40% sawdust, 40% wheat, 20% coffee grounds, but oysters will eat almost anything as long as the substrate is not to wet and not to dry)
-filter wool like used for aquaria
-spray bottle
-disinfectant (70%alcohol works fine)
first you need to make a substrate. I cook the wheat until lots of the grains burst (around 30min), sieve them, and use the cooking water to soak the sawdust. leave both grain and sawdust to drip off for 10 minutes and then mix it with the DRY! coffee grounds.
like I said before you can use almost anything as substrate, but it's really important that your mushrooms have enough water, but all of the water should be taken up by the substrate.
I fill this substrate into jars with a hole in the cap for pressure release during sterilisation. For a filter I use standard filter wool for aquaria, but I will make a picture later to show you what I mean
Then I sterilise these for 60-70min in the pressure cooker.
When you came that far the only remaining problem is a sterile inoculation.
I use small bits from the interior of the mushroom, because the fruiting body of the mushroom is only a generative state of the mycelium which can go back to a vegetative state within a day. What's also interesting is, that the interior of the mushroom is always sterile, so if you manage to transfer a bit of it onto sterile substrate without polluting it with yeast or mould spores it will just colonize the substrate and also you get a clone which has exactly the same DNA (and also the same growing characteristics) than it's parent
Last problem of contamination is air, because there are always thousands of spores flying around, but with a little water and a little help from gravity there's also an easy solution for that. You need a small room (bathroom works fine for me) and a spray bottle, cleaned and filled with fresh water. If you spray all the room with water for some time (I spray for about 5 minutes in a room of only 4m²) all the contaminations will bind to these millions of small water drops and slowly sink to the floor, so you should wait another 5 minutes so everything has reached the ground before you start working. !DON'T LEAVE THE ROOM, DON'T OPEN THE DOOR, DON'T OPEN A WINDOW!
Now you have sterile substrate, sterile inoculation material from the interior of a mushroom and a room without any airborne contaminations - > everything sterile, everything good so far
Now you clean the surface you will work on with the disinfectant, clean the glasses all around with the disinfectant and do the same with a sharp knife you should have prepared.
now use only a little bit of disinfectant to kill spores on the outside of the mushroom and rip it in two pieces to expose parts which haven't come into contact with airborne contaminations. take the knife and hold the blade in a lighter flame for some seconds and cut out a little piece from the interior of the fruiting body, open the jar a little bit and throw in the mycelium. I burn the blade after every jar to be really on the save side.
now just leave the substrate at room temperature for 2-5weeks (depending on mushroom species, jar size, temperature...) and the mycelium should have colonized the whole substrate. Now you can use this substrate to inoculate logs or new substrates. For growing more substrate you just sterilise new jars and only a grain of colonized wheat is sufficient to produce another litre of substrate!
I hope everything is written understandable, if not just ask, but explaining stuff like that in a foreign language isn't that easy for me
In this
thread you can see pics from my pholiota nameko and hericum growing at the moment
https://permies.com/forums/posts/list/120/21211