【化】 乳酸发酵
【医】 乳酸发酵

Lactic \Lac"tic\, a. [L. lac, lactis, milk: cf. F. lactique. See
{Lacteal}, and cf. {Galactic}.] (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}.
[1913 Webster +PJC]


Fermentation \Fer`men*ta"tion\ (f[~e]r`m[e^]n*t[=a]"sh[u^]n), n.
[Cf. F. fermentation.]
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 {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.

Note: In industrial microbiology fermentation usually refers
to the production of chemical substances by use of
microorganisms.
[1913 Webster +PJC]

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 [rarr] H2O +
C2H4O

Note: Alcohol. Water. Acetaldehyde. 2. C2H4O + O [rarr]
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
Torul[ae] 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}.