What role does yeast play in the brewing process?

Yeast plays a crucial role in the brewing process primarily by fermenting sugars present in the wort. During fermentation, yeast consumes these sugars and converts them into alcohol and carbon dioxide. This transformation is essential not only for increasing the alcohol content of the beer but also for developing flavors and aromas that contribute to the overall profile of the final product. Different strains of yeast can impart distinct characteristics, influencing the taste and complexity of the beer.

The other choices highlight processes or functions that are not directly related to what yeast does. For instance, yeast does not serve to clarify the beer after fermentation; while certain yeast characteristics can affect clarity, clarification is usually achieved through filtering or fining processes. Additionally, yeast does not provide nutrients to the malt; malted grains are typically rich in nutrients that support yeast activity. Finally, yeast does not directly decrease bitterness in beer; the bitterness is primarily influenced by the hops used in the brewing process. Thus, the fermentation of sugars to produce alcohol is the fundamental and defining role of yeast in brewing.