Thenard stated that yeast was the cause of fermentation, and held it to be of an animal nature, since it contained nitrogen and yielded ammonia on distillation, nor was it conclusively proved that the yeast cell was the originator of fermentation until the researches of C. Cagniard de la Tour, T.
These investigators regarded yeast as a plant, and Meyer gave to the germs the systematic name of "Saccharomyces" (sugar fungus).
It is clear from Liebig's publications that he first regarded yeast as a lifeless, albuminoid mass; but, although later he considered they were living cells, he would never admit that fermentation was a physiological process, the chemical aspect being paramount in the mind of this distinguished investigator.
In 1857 Pasteur decisively proved that fermentation was a physiological process, for he showed that the yeast which produced fermentation was no dead mass, as assumed by Liebig, but consisted of living organisms capable of growth and multiplication.
The preference exhibited by yeast cells for sugar molecules is shared by mould fungi and soluble enzymes in their fermentative actions.
In 1897 Buchner submitted yeast to great pressure, and isolated a nitrogenous substance, enzymic in character, which he termed "zymase."
This body is being continually formed in the yeast cell, and decomposes the sugar which has diffused into the cell.
In this respect the plasma behaves in a similar manner towards the sugars as does the living yeast cell.
About this time Hansen, who had long been engaged in researches on the biology of the fungi of fermentation, demonstrated that yeast free from bacteria could nevertheless occasion diseases in beer.
Duclaux stated that the yeast question as regards low fermentation has been solved by Hansen's investigations.
This method obtains when yeast is vigorously fermenting a saccharine solution.
The yeast plant and its allies are saprophytes and form no chlorophyll.
The beer yeast S.
The formation of spores is used as an analytical method for determining whether a yeast is contaminated with another species, - for example: a sample of yeast is placed on a gypsum or porcelain block saturated with water; if in ten days at a temperature of 52° F.
No spores make their appearance, the yeast in question may be regarded as S.
In the zymo-technical industries the various species of yeast exhibit different actions during fermentations.
It has not, however, been possible to transform a typical top yeast into a permanent typical bottom yeast.
This body has been prepared from active yeast, and from fruits and other parts which have been kept for some time in the absence 01 oxygen.
It may also take place where rapid proliferation of the cell is going on, as in the budding of the Yeast plant.
Cell budding takes place in yeast and in the formation of the conidia of Fungi.
Some observers consider that the yeast nucleus possesses a typical nuclear structure, and exhibits division by mitosis, but the evidence for this is not very satisfactory.
Of the greatest importance is the alcoholic fermentation brought about by yeast cells (Saccharomyces cerevisiae seu vini); this follows the equation CH120 6 =2C 2 H 6 0+2CO 2, Pasteur considering 94 to 95% of the sugar to be so changed.
The principal industries include tanning, dyeing, tile-making, milling, the production of yeast and there is a large establishment for the manufacture of railway stock.
The vomiting may take place every two or three days, enormous quantities of undigested food mixed with frothy, yeast-like mucous being thrown up. And whilst the stomach is slowly filling up again after one of these uncontrollable emptyings, sudden and violent movements of the individual may cause the fluid to give rise to audible "splashings."
In course of an investigation in 1822-1823 on the effects of heat and pressure on certain liquids he found that for each there was a certain temperature above which it refused to remain liquid but passedintothegaseous state, no matter what the amount of pressure to which it was subjected, and in the case of water he determined this critical temperature, with a remarkable approach to accuracy, to be 362° C. He also studied the nature of yeast and the influence of extreme cold upon its life.
It was, for nearly two years after this, rye and Indian meal without yeast, potatoes, rice, a very little salt pork, molasses, and salt; and my drink, water.