Have you ever considered using beer, wine, or even champagne yeast to make sourdough bread with? A lot of sourdough baking enthusiasts do that. The different strains of yeast give different flavor characteristics to sourdough breads. You can even use a bread machine to make sourdough bread these days! I know, because I've just published an eBook on the subject! It's called, "Bread Machine Sourdough," and is available in both Amazon Kindle and EPUB (for the Nook eBook reader)formats. Right now, you can find it on either Amazon or Lulu, bit it should also be available on the iBookstore and Barnes and Noble before long.