Yeast is the microorganism responsible for fermentation in beer. It consumes sugars from malt and produces alcohol and carbon dioxide. There are two primary categories of brewing yeast: ale yeast (Saccharomyces cerevisiae) and lager yeast (Saccharomyces pastorianus). Each type contributes distinct flavors and fermentation characteristics. Yeast can also add fruity esters or spicy phenols depending on strain and fermentation temperature.
