Which ingredient in beer is responsible for fermentation?

The ingredient responsible for fermentation in beer is yeast. Yeast is a microorganism that consumes the sugars present in the malt and converts them into alcohol and carbon dioxide during fermentation. This process is what allows beer to develop its alcohol content and contributes to the development of distinct flavors and aromas.

Malt provides the sugars necessary for fermentation, and while water is the primary ingredient in beer and hops add bitterness and aroma, it is yeast that actually carries out the fermentation process, making it a crucial component in beer production.