Sorry i know about koji didn't realize sake was made strictly from it. I don't know where the yeast balls are traditionally used, though there is a thread on here called"traditional chinese rice wine" that uses them.They do have some kind of mold(could be koji for all i know)in them as they act the same as koji, not only fermenting the available sugars, but also taking care of saccrification. But im looking to make other products with them, not rice wine anyway. Just wanted to know if anyone used them with anything other than rice.
Traditionally koji is the only thing that was used in fermentation traditionally in Japan with the single exception of Natto, which is fermented with bacillus subtilis bacteria, which naturally was found in the rice straw it was wrapped in. Natto is still fermented with bacillus subtilis, just as starter cultures now instead of by wrapping them in straw. Sake in Japan is only made with koji. Ironically there was a Japanese scientist near the turn of the century who thought koji was the ultimate fermentation organism and wanted to get all of the brewers in North America to use koji mold instead of yeast to brew beer. Of course, the brewers rejected him when he approached them with the idea.
I imagine you might find some people outside of Japan making something that they call "sake" out of yeast or bacteria, but in Japan it is solely made from koji.
Part of the reason is that Japan didn't even know about the existence of yeast until after the 1860s because the entire country had been closed off from the outside world. That may have something to do with the fact that the only fermentations in Japan done with yeast are originally Western things such as beer and bread.
I can't comment on China, but I do know that all traditional Chinese fermentation was done with mold and not yeast, but I'm not sure when yeasts started to be used in China. You'll find that the majority of East Asian fermentation is based off of molds and most commonly koji (which in some countries, such as Japan, was the only mold used pretty much).
This explanation is getting long, BUT... Theoretically you could use molds such as koji to brew beer, make wine, mead, and so on. The flavor is very likely to change and I've never heard of anyone using koji in beer before. But as I mentioned above, there was a scientist who tried to convince the US beer companies to use koji mold instead of yeast for their beers. So it might be worth trying out.
EDIT:
This is the scientist, although wikipedia doesn't mention the anecdote I gave:
http://en.wikipedia.org/wiki/Jokichi_Takamine