Which compound is split off during ethanol fermentation and released as a byproduct?

During ethanol fermentation, one of the key processes that occurs is the conversion of glucose to ethanol and carbon dioxide. This fermentation pathway is vital for certain microorganisms, including yeast, which converts sugars into alcohol and gases under anaerobic conditions.

As glucose is metabolized through glycolysis, it is broken down into two molecules of pyruvate. These pyruvate molecules are then further processed in the fermentation pathway. The pyruvate is decarboxylated, which means that a carbon atom is removed from the pyruvate in the form of carbon dioxide (CO2), resulting in the production of acetaldehyde. This acetaldehyde is then reduced to ethanol in a subsequent step.

The release of carbon dioxide as a byproduct during this decarboxylation step is a hallmark of ethanol fermentation, contributing to the bubbles seen in fermenting beverages and the rise of dough in baking. Therefore, CO2 is correctly identified as the compound that is split off and released during the fermentation process.