What a coincidence! I was literally just last night watching a documentary about sourdough bread and was considering giving it to my bugs. I was going to bake it, though, but it's probably better not to keep the microbes. I'm totally going to try this. I think I'll try one colony with the fermented wheat bran and one colony with sourdough.
EDIT: I was taking a closer look at the article just now. It's too bad that yeast don't like sucrose very much. Glucose seems kind of expensive. If anyone know where I can order glucose for cheap, I would love to know.
I'm also wondering about substitutions. From what I read, yeast grow best on maltose and second best on glucose. I was looking into natural sources of maltose and cooked sweet potatoes contain it. Sweet potatoes also have other good stuff, so I wonder if this could be a good addition to the mix? It might give you a better yield of yeast and other microbes as well as increasing the general nutrient content of the mash. Sweet potatoes are sort of cheap. I haven't done the math, but they might even be good as just a supplement. Use glucose/maltose, but maybe a couple times a month cook and mash a sweet potato and mix it in. I dunno. Just speculating.