I've always been very careful to keep my "other" fermenteds like sauerkraut, cheese, vinegar, sourdough starter, etc, FAR away from my beer.
Remember that it's cultures like lactobacillus that ferment your cheese. You want to avoid cross contamination, unless you love sour beers.
I realize that a keg is sealed, but I still wouldn't risk that. In a carboy or bucket during fermentation, I would be even more cautious.