What is the primary byproduct of fermentation besides ethanol?

The primary byproduct of fermentation, in addition to ethanol, is carbon dioxide. This process occurs during anaerobic respiration when microorganisms, such as yeast, convert sugars into energy in the absence of oxygen. As yeast ferments the sugars, it breaks them down into ethanol and releases carbon dioxide gas as a result of the metabolic process.

This is particularly evident in processes such as bread-making, where the carbon dioxide produced causes the dough to rise, creating a light and airy texture. The production of oxygen is not a byproduct of fermentation; rather, it occurs during photosynthesis. Water can be produced in various biological processes but is not a primary byproduct of fermentation specifically. Methane is generally produced through anaerobic digestion by different organisms, not the typical yeasts used in fermentation.