Bread-Bakers v103.n006.1

I am looking for information regarding the practice of making bread with 
Hop Yeast. I have a couple of recipes but I can't find any information 
about the role of the hops. As far as I understand it, the actual leavening 
process comes from the reaction of the potatoes and sugar, so why add hops?

Best wishes from Australia,
Silke Hartmann