I love kombucha and use that to make my starter for sour dough bread. I like Kefir but very time I bought it, it would mold up pretty fast.
Interesting. We like sour dough bread but never wanted to get a sourdough starter started. Did not think of kombucha - clever! If you bought your kefir ready bottled at the store we found Lifeway Kefir to be a very good brand.