fermentation

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The anaerobic conversion of sugar to carbon dioxide and alcohol by yeast.
2. n. Any of a group of chemical reactions induced by living or nonliving ferments that split complex organic compounds into relatively simple substances.
3. n. Unrest; agitation.

Century Dictionary and Cyclopedia

1. n. A gentle boiling or ebullition.
2. n. A decomposition produced in an organic substance by the physiological action of a living organism or by certain unorganized agents. See ferment. Fungi (and especially species of Saccharomyces) and bacteria are the agents of fermentative processes or changes. Fermentation naturally ceases when the nutritive elements of the fermented substance are exhausted, or a sufficient proportion of a substance (as alcohol) deleterious to the ferment-organism is produced. It may be checked or altogether prevented by anything which prevents the growth of the organism, as by exclusion of the germs or spores, by subjection to a temperature too high or too low, by the presence of too large a proportion of sugar or of a substance (called an antiseptic) which acts as a poison to the organism. There are various kinds of fermentation, each of which is caused by special organisms. Alcoholic fermentation in saccharine solutions, or fermentation in its most restricted sense, may be produced by any of several organisms, including several species of Saccharomyces, Mucor, Penicillium, and Aspergillus. and to a slight extent by certain other fungi; but the most important agent is Saccharomyces cerevisice, which produces the fermentation of beer. In fermenting wine, several species of Saccharomyces are found. S. Mycoderma forms a mold-like growth on the surface, the so-called flowersof wine. Acetous fermentation takes place in liquids which have undergone alcoholic fermentation, and is caused by Micrococcus (Mycoderma) aceti, the vinegar-plant. The alcohol is oxidized, and acetic acid or vinegar is the result. This micrococcus takes two forms: the immersed or anaërobiotic form exists as a mucilaginous mass called the mother of vinegar; the other is the surface or aërobiotic form, the flowers of vinegar. According to Pasteur, the latter only is active in producing fermentation. Lactie fermentation, or souring of milk, is induced by certain bacteria which decompose the sugar of milk and produce lactic acid. Viscous fermentation is of two kinds: the one is caused by certain bacteria which convert the fermenting substance into a slimy mass and produce mannite; the other is caused by Leuconostoc mesenterioides, which brings about the slimy condition, but does not produce mannite. The latter occurs in saccharine solutions, and is a source of serious loss to sugar-manufacturers on the European continent. The agent in butyric fermentation is Bacillus amylobacter, and butyric acid is the result. Certain fermentative changes are produced in wood by various fungi. Putrefactive fermentation, or putrefaction, occurs in animal substances and plant products containing a large proportion of nitrogenous matter. The organism which is active in the putrefaction of beef is Bacterium termo. The ammoniacal fermentation of urine is caused by Micrococcus ureæ. See putrefaction, bacterium, and germ theory, under germ.
3. n. Figuratively, the state of being in high activity or commotion; agitation; excitement, as of the intellect or feelings, a society, etc.
4. n. See the adjectives.
5. n. Synonyms See ebullition.

Wiktionary

1. n. biochemistry Any of many anaerobic biochemical reactions in which an enzyme (or several enzymes produced by a microorganism) catalyses the conversion of one substance into another; especially the conversion (using yeast) of sugars to alcohol or acetic acid with the evolution of carbon dioxide
2. n. A state of agitation or excitement; a ferment

GNU Webster's 1913

1. n. (Physiol. Chem.) The process of undergoing an effervescent change, as by the action of yeast the transformation of an organic substance into new compounds by the action of a ferment{1}, whether in the form of living organisms or enzymes. It differs in kind according to the nature of the ferment which causes it.
2. n. A state of agitation or excitement, as of the intellect or the feelings.

WordNet 3.0

1. n. a state of agitation or turbulent change or development
2. n. a process in which an agent causes an organic substance to break down into simpler substances; especially, the anaerobic breakdown of sugar into alcohol