F. W. TANNER 505 



FORMATION OF FAT 



Much work has been done on the fats of the yeast cell, but until quite recently 

 comparatively little has been done with the species which produce larger amounts. 

 The early work is discussed in the several texts on yeasts. Paul Lindner was one of 

 the first to show that fat could be made with yeasts. Among several fungi studied, 

 Lindner isolated Endomyces verualis, a fungus which, although not a true yeast, may 

 be properly discussed in this chapter. The fungus ordinarily grows with a mycelial 

 vegetation almost devoid of fat. When, however, the hyphae break up into segments 

 which bud like yeasts, fat production begins. By cultivating it in thin layers on the 

 surface of suitable media the fat content may increase to as high as 28 per cent in 

 fifteen days. Fat formation by this fungus was also studied by Nadson and Kono- 

 kotina/ members of a commission appointed in Russia to investigate the possibility of 

 making fat with yeasts. Diluted molasses with added ammonium sulphate was found 

 to be a good medium in which to propagate the fungus for fat formation. The fat 

 produced by Endomyces vernalis is a yellowish liquid resembling olive oil in appear- 

 ance and flavor. The chief constituent is triolein, but free fatty acids are also present. 



Another fat-forming yeast from soil was announced by De Jong- in 1926. Each 

 cell was found to contain a large globule later demonstrated to be fat. The species was 

 named Tonila lipojera. Fat formation was not noticed in the cell until after fourteen 

 days' incubation. 



A valuable series of contributions on this subject has come from Maclean^ and her 

 colleagues. They reported small amounts of fat in normal yeast; increased fat in 

 yeast which was old and degenerated. This fat was said to be in union with the cell 

 matter and not extractable from it by alcohol or ether. In the second contribution^ 

 they showed that fat in the yeast cell was formed from carbohydrate. They showed 

 also that the addition of alkali phosphates to a carbohydrate solution increased the 

 amount of fat which was stored. If the proportion of sugar was varied in a medium 

 containing a certain definite amount of phosphate, the amount taken up by the yeast 

 cell varied with the sugar. Fisher suggested years ago that carbohydrate molecules 

 condensed to form straight chains which by reduction and oxidation were changed 

 into fatty acids. This hypothesis has not been generally accepted. In 1921, Lindner^" 

 suggested that alcohol molecules might condense in the cell to form straight-chain 

 compounds which by subsequent oxidation formed the straight-chain fats. Lindner 

 noticed that when yeast was incubated in a solution containing ethyl alcohol more 

 fat was deposited in the cell. 



Maclean and Hoffert studied the availability for fat manufacture of a number of 

 carbon compounds. They found that yeast could utilize a number of compounds in 

 aerated media for building fat but could not utilize other closely related substances. 

 They believed that the evidence obtained from a study of yeast was distinctly against 



'Nadson, G. A., and Konokotina, A. G.: Wchnsch. Bran., 41, 249-51. 1924. 



^Dejong, L. E. Den: Nederl. Tydschr. v. Hyg. Microb., i, 136. 1926. 



3 Maclean, I. S.: Biochem. J., 16, 370-79. 1922. 



''Maclean, I. S., and Hoffert, C: ibid., 17, 720-41. 1923; 18, 1273-7S. 1924; 20, 343-57. 1926. 



5 Lindner, P.: Ztschr. lech. Biol., 9, 100. 1921. 



