so I have some berliner weisse in the primary with a pure lacto culture and yeast. Think I could take some yeast off the bottom for a good culture in which to make sourdough with? Maybe some spent grains in the bread for good measure?
Sourdough is created by Lactobacillus, Acetobacter, and Saccharomyces exiguus (wild yeast). I'm no professional baker but I'm thinking since the flavors depend on a natural balance of the 3, a lacto culture might be overkill. You could always try one loaf fermented naturally and one with the lacto culture though and compare 'em.