New wild culture sourdough starter from Prague

Just captured a new sourdough starter culture in Prague, Czech Republic.  The first loaf was a lovely wheat with solid rise for a baby, and now, I'm feeding the culture whole rye and buttermilk to make a classic Eastern European Pumpernickle loaf.  This sourdough starter from Prague is going to be a great wild culture for home baking!

Feeding the culture with buttermilk? I've never heard of such a thing. Have you done this before? How does it effect the flavor?