Fermentation

Fermentation is when a cell uses sugar for energy without using oxygen at the same time. Fermentation is also when oxidation occurs in the absence of oxygen.   

'Fermentation' also describes growing microorganisms on a growth medium. This is done to get a chemical product. French microbiologist Louis Pasteur studied fermentation and the microorganisms that cause it. The science of fermentation is known as zymology.

Yeast is an organism that ferments.  When yeast ferments sugar, the yeast uses sugar and produces alcohol.  The process uses the coenzyme NAD: In metabolism, NAD helps redox reactions, carrying electrons from one reaction to another. Fermentation is a less efficient form of respiration than oxidative respiration (respiration using oxygen).

The ethyl alcohol produced by yeast is used to make beverages or biofuel. Yeast can be also used to grow bakery products like bread and cakes faster. In some cases yeast might be used to speed up the process of creation of wine.

Other cells make vinegar or lactic acid when they ferment sugar.  In a different way, the fermentation process can continue and turn the alcohol into vinegar i.e. acetic acid.

 Types of fermentation 
When yeast ferments, it breaks down the glucose (C6H12O6) into ethanol (CH3CH2OH) and carbon dioxide (CO2).
 Ethanol fermentation always produces ethanol and carbon dioxide. It is important in bread-making, brewing, and wine-making.
 Lactic acid fermentation produces lactic acid. It happens in muscles of animals when they need lots of energy fast. The pain of a cramped muscle is caused by the build-up of lactic acid. The pain eases as the product is taken away by the blood supply.

 Other websites 
 Fermentation (biochemistry) -Citizendium

 References 
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Category:Fermentation
Category:Food science