Bacteria might be a key to trigger fruiting, but sterilized or pasteurized, any casing almost instantly develops huge numbers of bacteria once laid out over a colonized substrate. I have read that the common button mushroom requires specific bacteria and in large numbers to promote pins which is why they only fruit well if the casing is pasteurized. But I see no evidence of this with cubensis or Pan Cyans. Why? Because I sterilize my casings and I did not see a huge problem with my flushes of either. Now before you say they could have been better, maybe you should take a look at them in the attachment. How much better could they be? The cubensis tray in particular didn't have room for another mushroom. The Pan Cyans weren't the best possible, but the trays there couldn't be too far off the mark. I think Pan Cyans need a casing for some reason, but there is no reason to not sterilize the casing. Cubensis can fruit in any way possible.