There are two main types of beer yeast: bottom-fermenting yeast, Saccharomyces uvarum (lager fermentation), and top-fermenting yeast, Saccharomyces cerevisiae (ale fermentation). Their way-of-working is identical as they both absorb sugars present in the fermentation tank (melibiose for lager fermentation, fructose for ale fermentation) and then turn them into alcohol.
