Respiration is a process that produces energy by the breakdown of molecules within the cell. It contains a large number of complex reactions, each one is catalyzed by an enzyme. When the molecules break down, energy that has been stored in their chemical bonds are released. Cellular respiration provides the energy for such additional functions as muscle contraction and the generation of electrical impulses. For example, simple food substances such as glucose are broken down and the energy that they contain is released. Respiration produces 38 ATP from one glucose molecule, making it a very effecient method for generating energy.
Fermentation is a process that does not require oxygen, uses glucose as a reactant, and produces ATP and a compound as the product. Lactate bactria forment milk producing yogurt and gives the yogart a sour taste. Fermentation produces less energy than aerobic respiration and produces energy directly from glucose. If fermentation occurs in a closed container, the build up of carbon dioxide will stop the reaction and produce a product like root beer which has virtually no alcohol in it. At the end of fermentation the container may be sealed producing a carbonated alcololic beverage such as beer.
David E.Green Respritaion, vol.20,Collins encyclopedia
cd rom 28 Feb. 1996.