i86 



PHYSIOLOGY OF NUTRITION 



ture in beer-wort is transferred to gelatine and the cells multiply and develop 

 into giant colonies upon the gelatine surface. The form of colony is always con- 

 stant for the same species and different forms of colonies are produced by 

 different kinds of yeast. The drawings of Fig. ga show how distinct are the 

 giant colonies of various different yeasts. 



I It has been seen that alcohoUc fermentation is a process involving the action 

 of enzymes^ (see page 184). Besides carbohydrates, such ketonic adds as pyro- 

 tartaric acid may also be decomposed in this way, as was shown by Neubergi 

 and his co-workers. Pyrotartaric add is spht into carbon dioxide and acetic 



S. pastorianus I. S. pastorianus II. 



S. pastorianus III. 



S. elUpsoideus I. 



Pig. 90.- 



5. elUpsoideus II. Bottom-Fermentation Yeasts. 



-Giant colonies of different yeasts. {After P. Lindner.) 



aldehyde, by a special enzyme, carboxylase, the reaction being represented by 

 the following equation: 



Carbon 

 Pyrotartaric acid dioxide Acetic aldehyde 



CH3COCOOH = CO2 H- CH3COH. 



The acetic aldehyde thus formed is reduced to ethyl alcohol. Kostychev^ re- 

 ports that pyrotartaric add is apparently one of the intermediate products in the 

 breaking down of glucose. Zaliesskii' found the enzyme carboxylase in higher 

 plants. 



Reductase is plentiful in yeast, and this enzyme has been shown to play an 



■ Neuberg, C, and Karczag, L., Ueber zuckerfreie Hefegirungen. IV. Carboxylase, ein neues'Enzym 

 der Hefe. Biocbem. Zeitsch. 36 : 68-75. 1911. Idem, same title. F. Zur Kenntnis der Carboxylase 

 Ihtd. 36: 76-81. 1911. Neuberg, Carl, and Kerb, J., Entsteht bei Zuckerfreien Hefegftningen /Ethyl- 

 alkohol? Zeitsch. Garungsphysiol. 1: 114-120. 1912. 



2 Kostytchew, S., Ueber Alkoholgarung. (I Mitteilung.) Ueber die Bildung von Aceteldehyd bei der 

 nlkoholisohen Zuckergftrung. Zeitaoh. physiol. Chem. 79: 130-14S. I9I2. Kostyschew, S., and Hub- 

 benet, E. (11 Mitteilung.) Ueber Bildung von Aethylalkohol aus Acetaldyhyd durch lebende und getOtete 

 Hefe. Ibid. 79 : 359-374. 191a. 



« Zaleski, W., Ueber die Verbreitung der Carboxylase in den Pflanzen. Her. Deutsch. Hot. Ges. 

 31 : 349-353. 1913. 



• This and the next following paragraph are not in the German edition and are translated 

 from the 7th Russian edition. — Ed. 



