I think what Rat means
wow, thanks for that insight.
However, just to let you know, you have it all wrong.
Yeast doesn't contribute to the flavour of the sourdough, the bacteria does. The bacteria and the acids they produce is what creates the distinctive flavour. Further to your comment, yeast is everywhere it is one of the most prevalent organisms in the world (besides bacteria etc), as common as dust. As such, any "sourdough" no matter its source, when moved is overtaken with local strains of bacteria and yeast of the new location.
So what you think Rat means, is wrong, yes his buddy has an aged sourdough starter, but thats all it is, it originated from SanFran and thats Rat's claim to fame, whereas in reality its probably been moved a dozen or more times and has no more semblance to a SanFran sourdough than my own.
Now, onto what yeast "eats" its not glucose and sugars, it is technically "carbohydrates" which includes starches as well. In the case of sourdough where there is no added sugar, yeast specifically eats the starches in the flour, as well as free sugars (few and limited in refined flour).
And yes, yeast is DEFINITELY used in distilling (no maybes there, I do my own distilling).