A general definition of fermentation is an energy-yielding anaerobic metabolic process in which organisms convert nutrients (typically carbohydrates) to alcohols and acids (lactic acid and acetic acid).
The most commonly known definition for fermentation is the conversion of sugar to alcohol, using yeast, under anaerobic conditions, as in the production of beer or wine, vinegars and cider. Fermentation is among the oldest of historical biotechnological processes that people have been using for thousands of years.
However, in biotechnology, the term is used more loosely to refer to growth of microorganisms on food, under either aerobic or anaerobic conditions.
Fermentation tanks, also called bioreactors, used for industrial fermentation processes are glass, metal or plastic tanks, equipped with gages and settings to control aeration, stir rate, temperature, pH and other parameters of interest. Units can be small enough for bench-top applications (5-10 L) or up to 10,000 L in capacity for large-scale industrial applications. Fermentation units such as these are used in the pharmaceutical industry for the growth of specialized pure cultures of bacteria, fungi and yeast, and the production of enzymes and drugs.
The art of studying fermentation is called zymology or zymurgy. Louis Pasteur was one of the first zymologists and referred to fermentation as “the result of life without air”.