What metabolic byproducts are produced by yeast when they need to eliminate excess waste?

When yeast undergo fermentation, especially under anaerobic conditions or when they experience stress, they produce metabolic byproducts as a means of expelling excess compounds from their cells. Ethanol is one of the primary byproducts formed during the fermentation process, which serves as an alcohol. However, when considering the specific context of yeast eliminating waste products, the production of esters is particularly relevant.

Esters are formed when an alcohol reacts with an acid. In brewing, yeast synthesizes esters during fermentation, often in response to various conditions such as the type of yeast used, the fermentation temperature, and the nutrients available. These compounds, which contribute to the flavor and aroma of the beer, are produced as a way for yeast to manage and mitigate the effects of their own metabolism.

Esters tend to be volatiles and can enhance the sensory characteristics of beer, providing fruity or floral notes that are desirable in many styles. Therefore, while other byproducts like alcohols, phenols, and ketones may also be produced during fermentation, the specific focus on esters aligns best with the question regarding the metabolic processes of yeast aiming to "eliminate excess waste."