I just tried it, and it was incredibly delicious! I cooked the beans, but I also used some uncooked ones, and both turned out to be very tasty. After fermenting for a while, I discovered that I could seal the lids without experiencing any additional pressure or carbonation.
I encourage you to give it a try yourself, whether using your old or freshly brewed kombucha. I haven't had a chance to taste the reddish SCOBYs yet, but I'm looking forward to it! Ü
Next step is to use them and make tempeh of them.
Edit: I used Feijão Preto CAMIL black beans.
You're in for a shitstorm, don't ferment beans.
That's not gonna remove their anti-nutrients only by boiling/steaming the fuck out of them.
Ferment red sauerkraut, excellent nutrition & put it in a sandwich.