Fermentation is the process by which living organisms recycle NADH→NAD+ in the absence of oxygen. NAD+ is a required molecule necessary for the oxidation of Glyceraldehyde-3-phosphate to produce the h...Fermentation is the process by which living organisms recycle NADH→NAD+ in the absence of oxygen. NAD+ is a required molecule necessary for the oxidation of Glyceraldehyde-3-phosphate to produce the high energy molecule 1,3-bisphosphoglycerate. Fermentation occurs in the cytosol of cells.