MASTERDOG Brewers Yeast Rich in B-Vitamins. Brewers yeast (saccharomyces cerevisiae) is rich in natural B-vitamins, minerals, amino acids and enzymes. It helps restore and maintain the natural flora in the gut, thus reducing gastro-intestinal disorder. Brewer’s yeast increases fibre digestion, making more nutrients available to absorb. The yeast cultures have been dried carefully to ensure they remain viable and maintain their full activity.