In my country, we also use a sour culture. We call it "Me". It is not a dough but a kind of dense sauce. We do not use it to make bread that is often used to make sour soup or stews. The way to make it looks like sourdough, but we use rice instead of wheat flour. It also does not need frequent feeding. Winter is about 2 weeks, summer is about 2-3 times. But I also know someone use it as bread yeast. I remember in the movie of Korean " the bread king" also mentioned this way.