54 PHYSIOLOGY OF YEASTS 



cellulose or a closely related substance, of an albuminous protoplasm 

 and a nucleus rich in nuclein. The yeasts contain hydrocarbons, 

 albuminoids, and fatty bodies. 



Let us consider successively these groups of substances. 



Hydrocarbon Materials: The analysis of Schutzemberger has 

 shown the presence of a substance like cellulose in the membrane, 

 which seems to be formed from sugar, and of a gummy substance 

 which seems to be transformed from this cellulose under the in- 

 fluence of the chemical agents used in its preparation. Finally 

 Errera and Clautriau l have disclosed the presence of glycogen which, 

 according to Laurent, is able to reach a concentration of 32 to 38 

 per cent. 



Fatty Bodies: Fats to the extent of 5 per cent of the dry material 

 have been reported. However, in old cells, the fat may increase 

 to even 20 per cent. This is not surprising, for we have stated that 

 it may exist in two forms: one as reserve products formed, without 

 doubt, from the sugars (Pasteur); the other seems to come from a 

 protoplasmic degeneration. The first is generally rare during fermen- 

 tation and appears especially during sporulation. The other is observed 

 in old cells in the state of degeneration. 



The fatty materials of yeasts are generally acid in reaction and 

 composed of ordinary fats, cholesterol, lecithin and phytosterol. 

 The weight of cholesterol may reach 0.06 per cent of the dry yeast, 

 according to Lowe, but increases in old cells. Hinsberg and Ross 

 have pointed out the presence of an ethereal oil, not saponifiable, 

 with a hyacinth odor to which he attributes the special odor of yeasts. 



Welter 2 in discussing a yeast which contains 50 per cent of 

 protein states that it contains 4 per cent of fat and this may be 

 increased up to 17 per cent. It is thought that the fat is produced 

 by a transformation of sugar. Bokorny 3 states that to secure 

 abnormal fat formation in yeasts, they must be fed quantities of 

 carbohydrates and proteins. From the data which he secured he 

 regards the cell protein as the source of the fat. Neuss 4 reports 

 a yeast which contained 18 per cent of fat on the dry basis. Under 

 special conditions of cultivation this could be increased to 50 per 

 cent. The fat was similar to olive oil. 



1 Clautriau, G. fitudes chim. du glycogene chez les champ, et les levures. 

 Ac. roy. de Belgique, 3, 1895. 



2 Welter, A. Yeast fat, a new source of fat. Seifenfabriken, 35, 845-6, 1915. 

 Chem. Abstracts, 10, 124, 1916. 



3 Bokorny, T. Yeast fat. Allgem. Brau-Hopfen Ztg. 55, 1803-5, 1915. 

 Chem. Abstracts, 10, 798, 1916. Assimilation of fat in plant cells, especially in 

 yeasts. Arch. Physiol. 1915, 305-49. Chem. Abstracts, 11, 2218, 1917. 



4 Neuss, O. Yeast fat. Seifenfabr. 36, 38, 1916. Chem. Absts. 10, 977, 1916. 



