Ok.
Once you have gotten a clean, pure mass of mycelium then you can distribute it into any (,reasonsble) bulk substrate.
The substrate must not be concentrated such that it will afford any competitor mold the same opportunity as your preferred mycelium.
When you do this, your mass of mycelium can be called "spawn".
Your substrate should be pasteurized in some way, that means bringing the temperature up to between 160 and 180 degrees for an hour or two or three, depending on your temperature.
What you will have done is killed most of the propagaules or spores of the competition. Likely you have preserved the beneficial or neutral organisms.
This state will last about two weeks. That means you have given your preferred organism a window of opportunity.
You will have "cooked" seeds, eggs, larvae and bugs as well.
This means that you should not put so little "spawn" into your substrate that it won't or can't fully colonize your substrate in that amount of time.
If you actually sterilize your substrate you have essentially reset it such that every organisms has the same chance to over take every other.
You dont want that.
Of course you can manipulate the ph of the substrate in order to land it in a window where that ph is favorable to your organism but unfavorable to undesirable organisms.
This is why I asked what the substrate is.
If you, say, wish to add your mycelium to cooked grain, it is very unlikely to work. Bacteria, the most rapidly growing organism will take hold first. Bacteria is not very mobile. Next will be any variety of lower fungi, pink, black, grey, green, blue, they will take hold and then sporulate quickly, spreading their spores to germinate again all while your mycelium has only just taken hold.
Good luck
