Brewer's yeast is a type of fungus formally known as Saccharomyces cervisiae. Along with other Saccharomyces species, brewer's yeast is used to brew beer and bake some breads, and can also be used as a nutritional supplement in an inactive form. 

Brewer's yeast is bitter in taste and should not be confused with baker's yeast. 

Nice article on all the uses, benefits and side effects here 

250g

From : Independent Irish Health Foods.