In addition to alcohol, what gas is a byproduct of glucose fermentation by yeast?

During the fermentation process carried out by yeast, glucose is broken down to produce energy. This biochemical process results in two primary byproducts: alcohol and carbon dioxide. When yeast ferments glucose, it converts the sugar into ethanol (alcohol) and releases carbon dioxide gas as a metabolic waste product.

Carbon dioxide is crucial in this context, especially in baking and brewing industries where it causes bread to rise and contributes to the effervescence in alcoholic beverages. The production of carbon dioxide during fermentation is a natural part of the yeast's metabolic process, alongside the creation of ethanol.

The other gases listed—oxygen, nitrogen, and methane—are not significant byproducts of yeast fermentation of glucose. For instance, oxygen is not produced in an anaerobic fermentation environment, which is the condition under which yeast operates when fermenting sugars. Nitrogen is an inert gas in this context, while methane is produced by other microorganisms, particularly in anaerobic digestion processes but not by yeast fermentation. Therefore, carbon dioxide is the only correct answer among the byproducts listed.