http://en.wikipedia.org/wiki/Nutritional_yeast
Apparently nutritional yeast is often Saccharomyces cerevisiae, which is one of the possible brewer's yeasts.
Anyway, I would not go on any yeast for B12, I would rather use seaweeds, as I wrote on the other post.
I would use yeast as a proteic integrator (we need to complement our main protein to get all the essential aminoacids we need) and source of minerals and B complex vitamins (but not B12).
Other foods are much more pleasant, and much more rich in B12.
Nutritional yeast, especially the malted one (where they add Malt in the process) is very pleasant, especially in salads and soups, but, as said, I would use it for other purposes..