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 Lac·tic a.  Physiol. Chem. Of or pertaining to milk; procured from sour milk or whey; as, lactic acid; lactic fermentation, etc.
 Lactic acid Physiol. Chem., a sirupy, colorless fluid, soluble in water, with an intensely sour taste and strong acid reaction. There is one center of optical activity, and this results in the observation of three isomeric modifications all having the formula C3H6O3; one is dextrorotatory (L-lactic acid), the other levorotatory (D-lactic acid), and the third an optically inactive mixture of the first two (DL-lactic acid); chemically it is 2-hydroxypropanoic acid.  Sarcolactic acid or paralactic acid occurs chiefly in dead muscle tissue, while ordinary lactic acid (DL-lactic acid) results from fermentation, such as the fermentation of milk by lactic acid bacteria. The two acids are alike in having the same constitution (expressed by the name ethylidene lactic acid), but the latter is optically inactive, while sarcolactic acid rotates the plane of polarization to the right.  The third acid, ethylene lactic acid, accompanies sarcolactic acid in the juice of flesh, and is optically inactive.
 Lactic ferment, an organized ferment (Bacterium lacticum or Bacterium lactis), which produces lactic fermentation, decomposing the sugar of milk into carbonic and lactic acids, the latter, of which renders the milk sour, and precipitates the casein, thus giving rise to the so-called spontaneous coagulation of milk.
 Lactic fermentation. See under Fermentation.
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 Fer·men·ta·tion n.
 1. The process of undergoing an effervescent change, as by the action of yeast; in a wider sense Physiol. Chem., the transformation of an organic substance into new compounds by the action of a {ferment1}, whether in the form of living organisms or enzymes. It differs in kind according to the nature of the ferment which causes it.
 Note: In industrial microbiology fermentation usually refers to the production of chemical substances by use of microorganisms.
 2. A state of agitation or excitement, as of the intellect or the feelings.
    It puts the soul to fermentation and activity.   --Jer. Taylor.
    A univesal fermentation of human thought and faith.   --C. Kingsley.
 Acetous fermentation or  Acetic fermentation, a form of oxidation in which alcohol is converted into vinegar or acetic acid by the agency of a specific fungus (Mycoderma aceti) or series of enzymes. The process involves two distinct reactions, in which the oxygen of the air is essential. An intermediate product, acetaldehyde, is formed in the first process.
 1.
 C2H6O  +  O →  H2O  +  C2H4O
 Note: Alcohol.           Water.   Acetaldehyde.
 2.
 C2H4O   +  O →  C2H4O2
 Note: Acetaldehyde.        Acetic acid.
 -- Alcoholic fermentation, the fermentation which saccharine bodies undergo when brought in contact with the yeast plant or Torula. The sugar is converted, either directly or indirectly, into alcohol and carbonic acid, the rate of action being dependent on the rapidity with which the Torulæ develop.
 Ammoniacal fermentation, the conversion of the urea of the urine into ammonium carbonate, through the growth of the special urea ferment.
 CON2H4 + 2H2O = (NH4)2CO3
 Note: Urea.  Water.   Ammonium carbonate.
 Note: Whenever urine is exposed to the air in open vessels for several days it undergoes this alkaline fermentation.
 Butyric fermentation, the decomposition of various forms of organic matter, through the agency of a peculiar worm-shaped vibrio, with formation of more or less butyric acid. It is one of the many forms of fermentation that collectively constitute putrefaction. See Lactic fermentation.
 enzymatic fermentation or Fermentation by an unorganized ferment. Fermentations of this class are purely chemical reactions, in which the enzyme acts as a simple catalytic agent. Of this nature are the decomposition or inversion of cane sugar into levulose and dextrose by boiling with dilute acids, the conversion of starch into dextrin and sugar by similar treatment, the conversion of starch into like products by the action of diastase of malt or ptyalin of saliva, the conversion of albuminous food into peptones and other like products by the action of pepsin-hydrochloric acid of the gastric juice or by the ferment of the pancreatic juice.
 Fermentation theory of disease Biol. & Med., the theory that most if not all, infectious or zymotic disease are caused by the introduction into the organism of the living germs of ferments, or ferments already developed (organized ferments), by which processes of fermentation are set up injurious to health. See Germ theory.
 Glycerin fermentation, the fermentation which occurs on mixing a dilute solution of glycerin with a peculiar species of schizomycetes and some carbonate of lime, and other matter favorable to the growth of the plant, the glycerin being changed into butyric acid, caproic acid, butyl, and ethyl alcohol. With another form of bacterium (Bacillus subtilis) ethyl alcohol and butyric acid are mainly formed.
 Lactic fermentation, the transformation of milk sugar or other saccharine body into lactic acid, as in the souring of milk, through the agency of a special bacterium (Bacterium lactis of Lister). In this change the milk sugar, before assuming the form of lactic acid, presumably passes through the stage of glucose.
 C12H22O11.H2O     -->     4C3H6O3
 Note: Hydrated milk sugar.         Lactic acid.
 Note: In the lactic fermentation of dextrose or glucose, the lactic acid which is formed is very prone to undergo butyric fermentation after the manner indicated in the following equation: 2C3H6O3 (lactic acid) --> C4H8O2 (butyric acid) + 2CO2 (carbonic acid) + 2H2 (hydrogen gas).
 Putrefactive fermentation. See Putrefaction.
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