what is fermentation
The acetaldehyde is then reduced into ethanol using the energy and hydrogen from NADH; in this process the NADH is oxidized into NAD+ so that the cycle may repeat (3). Fermentation is a metabolic process that converts sugar to acids, gases or alcohol.he acetaldehyde is then reduced into ethanol using the energy and hydrogen from NADH; in this process the NADH is oxidized into NAD+ so that the cycle may repeat (3). Fermentation is a metabolic process that converts sugar to acids, gases or alcohol.