Yeast
Yeast converts malt sugars into alcohol during fermentation. There are two types: bottom and top fermenting yeast. Beers fermented with bottom yeast are called lagers and those that use top-fermenting yeast are called ales. In 1886 in Amsterdam, Dr. Elion, a student of Dr. Louis Pasteur, discovered the famous Heineken A-yeast, a strain that is still used today only by Heineken.