fermentation processes that skate a little close to the edge for my taste

[eub]

The 1970s edition of Joy of Cooking gives a recipe for "salt rising bread", which is raised with a non-yeast ferment. This gives it "a dense crumb and favorable cheese-like flavor". The fermenting agent? Clostridium perfringens! So your bread is being raised by gas gangrene.

Besides gangrene, C. perfringens is known for causing food poisoning. Ensporulated, it can even survive boiling. Science says:

SRB starter samples were cultured at the University of Pittsburgh and abundant C. perfringens, type A grew out of all samples. However none of the cultures were positive for enterotoxin and thus would be unlikely to cause human food borne disease. While this does not preclude the possibility of other starter mixes containing enteropathogenic strains, the baking process appears to reduce bacterial contamination to safe levels and SRB has not been implicated in causing any human disease.

I'd try it from a bakery that makes it, but I might rather not culture my own starter.