|Memoir on alcoholic fermentation
1838 Charles Cagniard-Latour
|Cagniard-Latour, C. 1838. Memoire sur la fermentation vineuse. Annales
de chimie et de physique, Vol. 68, pages 206 222.
IT IS WELL KNOWN THAT WHEN FRESH beer yeast is mixed with a solution
of sugar and added to a closed flask . . . and exposed to a temperature
of 25¡ centigrade, very quickly, within a few minutes, the solution
undergoes a fermentation which proceeds very rapidly if the amount of yeast
added is considerable. However, when the solution does not contain the
yeast and the sugar in the solution is pure, the same circumstances do
not ensue, even after a very long time. It seemed important to examine
under the microscope this material which had the property of causing the
fermentation of sugar. This examination, which I have had the honour of
reporting in a letter to the Academy, has led me to consider that the particles
of which the yeast is composed are globular in form, and I have concluded
that it is very probable that these particles are organised. (Footnote:
Twenty-five years ago I first examined fresh yeast under the microscope.
However, my instrument was very poor, and I concluded that the yeast was
like a very fine sand composed of crystalloid particles. These observations
were in error. The majority of the microscopic observations indicated in
this memoir were performed on a microscope constructed by M. Georges Oberhauser.
It enabled me to obtain enlargements of 300-400 times. For measuring the
size of the globules, I used an ocular micrometer constructed by M. Charles
The globules which I have observed are generally simple, transparent,
spherical or slightly elongated, almost colourless. I have never seen them
exhibit any movement which could be considered an indication of their independent
action. On the other hand, the globules of yeast can appear in a liquid
before the alcoholic fermentation has begun. But when the globular bodies,
that is to say, the non-crystalline bodies, are beginning to produce themselves
in a mucous liquid which, before the experiment has begun, does not reveal
these globules, and when these bodies do not appear to have any power of
locomotion, the microscopist will consider these bodies as simple plants.
This is the way M. Turpin has viewed the protospheres which developed in
a gelatinous medium, as I have reported to the Institute in a previous
It is highly probable that the globules of yeast are organised, and
they appear to belong to the vegetable kingdom. . .
But these plants, if one can give this name to such simple vesicles,
are very small, and highly variable in size. The diameter of the largest
globules does not exceed a hundredth of a millimeter. For the most part
they are of such a size, that a cake of yeast of one cubic millimeter would
contain at least a million globules.
On the assumption that the yeast globules had the faculty to reproduce
themselves I performed a number of experiments to find out more about them....
My earlier observations (see the journal of the Institute, no. 185)
had yielded the following principal results: ( l ) In order to liberate
gas, the globules of yeast rise to the surface of the wort (of beer) and
many of these globules are within the foam or scum which is produced during
the fermentation, and can be readily observed with the microscope. ( 2
) During their action on the wort, the globules diminish in size, and very
probably produce seeds or reproductive bodies through this contraction,
since one discovers very soon in the wort new globules, smaller in size.
These globules, which are not observed at first, seem to have the ability
to reproduce by budding or elongation, and because of this can form globules
which confirms my hypothesis that the yeast globules are organised
and belong in the plant kingdom.
I examined samples removed hourly from the fermentation vessel. One
hour after the addition of the yeast I already saw that the wort contained
single globules each of which contained a small secondary globule attached
to it. This small globule seemed to grow, since a little while later most
of the pairs seemed to contain globules of the same size. The fourth sample
revealed a very few paired globules. In order to assure myself that these
pairs of globules were actually attached and not merely touching each other,
I applied a force to the cover glass with a small needle while watching
the globules under the microscope, and although this force produced a violent
agitation of the globules, it did not affect the point of attachment of
the pairs. It would appear that the individual globules become separated
naturally as they grow to a certain age, since the commercial yeast generally
consists of simple globules.... In the course of many fermentations which
I have carried out with beer yeast, it has been possible to distinguish
in certain (globules many granules, and sometimes a round or oval body,
sometimes central and sometimes lateral, which one can presume to be a
scar or umbilical mark which develops during the separation of the two
The globules of ferment are able to develop very rapidly, because when
one collects the total amount of yeast that is produced during the fermentation,
one finds that this quantity weighs about seven times the initial quantity
of yeast added, which agrees with the microscopic examination.
Considering the rapidity with which this increase in yeast is obtained,
there is every reason to believe that this is the result of the reproduction
of the globules of yeast which have been added. It appears that the globules
reproduce in a liquid which contains the nutrients favourable for their
growth. All brewers are aware that the beer wort ordinarily produces a
larger amount of yeast than that added, but it has been supposed that this
increase is due principally to a precipitation of the plant proteins which
are present in the wort....
But while the wort is a medium in which reproduction of the ferment
proceeds very readily, it is not the same as a simple solution of sugar,
since an active yeast does not increase in weight in the latter, and actually
loses its activity
M. Gay-Lussac has demonstrated in various experiments that oxygen has
a great influence on the beginning of fermentation in certain liquids,
especially in grape juice. But although oxygen is necessary for fermentation
to begin, it is not necessary for fermentation to continue. Because of
this fact and the knowledge that beer yeast is able to produce a fermentation
in sugary materials without the presence of oxygen, M. Gay-Lussac has advanced
the opinion that the power of fermentation rests in a large number of substances,
but in a different state than in beer y east. The experiments to he presented
below seem to indicate that this opinion is correct. I expressed the juice
from a bunch of grapes while they were enclosed in a bell jar under an
atmosphere of hydrogen and allowed this juice to remain under mercury for
more than 15 hours. During this time I examined under the microscope a
small amount of the deposit which separated from the juice and found it
to be practically amorphous. But after I allowed a small amount of oxygen
into the jar, which started the juice to ferment, I found a large deposit
of yeast globules. One can surmise the following from this: (1) The
bodies of these small plants form a part of the material which deposited.
(2) They had not germinated because they enclosed within the berries of
the grapes. ( 3) This germination begins when they are exposed to oxygen
and because of this beginning of development, they are able to act like
the beer yeast. It has been reported to me that it is possible to cause
the production of globules w hen egg white is diluted in water and heated,
and that the globules of yeast arise from a nitrogenous material of animal
or vegetable origin, which is present in the wort, and coagulates to form
the globules. If this is so the yeast globules are no more living than
those globules obtained during the coagulation of egg white by heat.
In order to clarify this point, I placed in a capsule in a bath heated
to 90° centigrade, a mixture of 50 grams of water and one gram of egg
white. When a portion of the albumin had been coagulated by the heat, I
removed the capsule and after cooling, examined a small amount of the material
which had formed at the surface of the liquid under the microscope. I found
that this material contained a type of globule with a diameter averaging
about a hundredth of a millimeter. But these globules resembled in general
something crystalloid, and in none of them could be seen granules or an
umbilical mark. It seems to me therefore, that the objection that the globules
of ferment are analogous to those of coagulated egg white is not valid.
Furthermore, I have conducted a spontaneous fermentation of wort in
a closed container, that is to say, a fermentation without the addition
of yeast. This wort, even though it had been filtered, produced during
its alcoholic fermentation a deposit of yeast. which upon examination under
the microscope, proved to be composed of globules analogous to those in
ordinary yeast. This fermentation took place much slower than those carried
out in breweries, and one might expect, if the hypothesis that the globules
are formed by a type of proteinaceous coagulation, that they would resemble
those from coagulated egg white. But this is not the case. The globules
in the deposit did not prove to be the same size as those in ordinary yeast,
hut this does not argue against their
living nature, since the fermentation in this case had taken place
over a very long time, and the globules may be quite different in age from
those in ordinary yeast.
I carried out the same experiment in a flask which had been filled
with carbon dioxide. Although the fermentation developed a little slower,
the deposit obtained showed the same appearance under the microscope.
Since in these experiments the deposit formed showed the same appearance
under the microscope as beer yeast, I have carried out a number of fermentations
in closed vessels with various liquids, such as currant juice, grape juice,
and prune juice, as well as in a solution of sugar with egg white. In all
these cases the liquids were filtered before they were placed in their
vessels. Examination of the deposits obtained has shown that in all cases
they are composed to a large extent of globules which are analogous to
those of beer yeast....
All who carry out fermentations on a large scale, such as brewers and
distillers, know that in spite of the greatest care in their operations,
their results are extremely variable. These irregularities are favourable
to the hypothesis that the alcoholic fermentation is caused by bodies endowed
with life, because who knows in how many different ways such similar bodies
can be affected....
I am acquainted with the principal literature concerning alcoholic fermentations
but I have seen no work in which the microscope was used to study the phenomena
on which it depends. (Footnote: Leeuwenhoek, in 1680, examined beer yeast
under the microscope and stated that it is composed of globules, but he
thouht they were a part of the grain which was used to make the wort. But
this observation did not suggest to this author the most important point,
that these globules are capable of germinating and growing in the wort
during the fermentation. )
The principal results of the present work are: ( I ) The beer yeast
is a mass of small globules which are able to reproduce, and consequently
are organised, and are not a simple organic or chemical substance, as has
been supposed. (2) These bodies appear to belong to the plant kingdom.
(3) They seem to cause a decomposition of sugar only when they are alive,
and one can conclude that it is very probable that the production of carbon
dioxide and the decomposition of sugar and its conversion to alcohol are
effects of their growth.
I would also like to remark that the yeast considered as an organised
body merits the attention of physiologists for the following reasons: (
I ) It can grow and develop under certain conditions very rapidly, even
under an atmosphere of carbon dioxide. (2) Its manner of growth presents
details of a type which has not been observed in other microscopic objects
composed of isolated globules. (3) It does not die w hen frozen or in the
absence of water.
In conclusion I would like to add that the old question of the cause
of alcoholic fermentation, which was proposed by the Institute, appears
to be solved from the present results and those I have reported in 18 3
5 and 1836. These results indicate the conclusion that in general ferments,
or at least those which cause alcoholic fermentation in the manner of yeast,
are composed of organised microscopic bodies which are very simple, and
the substances which they induce to ferment are purely chemical substances,
since they are sugar and compounds related to sugar.
Comment by Thomas Brock
This work was performed independently of Schwann's, and confirms his
for the most part. The student should note that the real reason these two
workers came up with the same observations at the same time was probably
due to the production of better microscopes, as Cagniard-Latour mentions.
Since the yeast cell is quite small in comparison to plant and animal cells,
it would take at least 400 magnifications to be able to discern cellular
details. It was this greater magnification which enabled Cagniard-Latour
to differentiate yeast cells from globules of coagulated egg albumin.
The author's observations on some of the physiological properties of
the yeast are interesting. The yeast cell's ability to grow anaeobically
and to withstand freezing and desiccation arc well confirmed today. Many
other microorganisms, including Some pathogenic ones, also possess these
This paper and the preceding one by Schwann gave Henle support for
his early germ theory of disease.