What is the primary role of yeast in brewing?

The primary role of yeast in brewing is to ferment sugars to produce alcohol and carbon dioxide. During the fermentation process, yeast consumes the fermentable sugars present in the wort and converts them into alcohol and CO2 as byproducts. This transformation is essential, as it not only contributes to the alcoholic content of the beer but also plays a crucial role in developing its mouthfeel and carbonation level.

While other factors, like carbonation, flavor, and clarification, play a role in the overall brewing process, these are secondary functions compared to the primary fermentative action of yeast. For instance, though yeast can indeed contribute to flavor and aroma through the production of various compounds during fermentation, its main and most critical function remains the conversion of sugars to alcohol and CO2.