Im thinking you innoculated the BRFcakes with a spore or liquid culture syringe? Looks like you have a pretty good technique and set up.
To me the attraction of growing oysters on cardboard is only that it can be done without using sterile technique and that the cardboard itself can theoreticaly be used as spawn. I Would say that the mycelium you have and the mushrooms its producing are gaining their nutrition, streangth and vigor from the BRF & coffee. If you pasteurized
straw and supplemented with coffee or bran your yeilds, nutritional content, and
medicinal quality of the shrooms would go up.
Cardboard supplies cellulose but there is nothing else really, but the thing is mushrooms need a little more nutrition to synthesize protiens and medicinal compounds to their full potentiel. Supplemented straw or sawdust provides that, plus it has the bonus of a biological community that will break down nutrients from the substrate for the mycelium plus synthesise benifical compounds for the mycelium directly and also indirectly by contributing antibiotic compounds to the substrate that act as an immune system for the mycelium.
The difference between sterilizing and pasteurizing is that when pasteurizing a in hospitable tempreture is held for a leangth of time in order to kill off certain organisms but it does not get hot enough to kill of certain benificial organisms.
Sterilization obviously is when all life forms are killed off.
When something is sterilized it is incredibly vulnerable to colonization from competitive organisms because the substrate is defenseless unless you ensure that they remain sterile until its innoculated and colonized by the innoculum like you did with the BRF jars. When something is pasteurized it is still colonized by the heat tolerant organisms and so will not readily contaminate in open air conditions.
Cardboard doesnt generally contaminate and is a selective substrate because its lack of nutrients dont facilitate growth in most fungi species and doesnt offer simple sugars for bacterial growth. It can contaminate though.
Oysters tear through it because they are a primary decomposer and can break complex things down that have not been previously broken down by another organism.
Portabella on the other hand needs a substrate to have been previously broken down and would not thrive on card board, and coffee unless in minute ammounts would probably be too nutritious for ports which would slow the growth.
Sorry for rambling and I hope this post doesnt come across as offensive or discouraging. Im pretty impressed seing your
project and am just thinking that if youd done the same thing using straw youd be pretty happy with the results. So Id like to encourage you to use your skills to their full potential.