392 MICRO-ORGANISMS AND FERMENTATION. 



about beer turbidity or reduce the stability of beer, even 

 when vigorous cultures are added to the beer as prepared 

 for consumption, if it is kept in well-filled and stoppered 

 bottles. If Torulas are added in minute quantity at the 

 beginning of storage, they display no development during 

 storage, and die off towards the close. It is clear that their 

 development is not hindered by the quantity of alcohol pro- 

 duced, from the fact that they grow in yeast-free beer with 

 access of air. It is rather the lack of oxygen and the quantity 

 of carbon dioxide present that are accountable for their 

 suppression. 



In respect to the reaction of the Torulas on the sugars, 

 Will proved that the small-scale fermentation method of 

 P. Lindner is not applicable. The question to be solved is 

 whether an organism entirely lacks the power of fermenta- 

 tion, or whether a given sugar is unfermentable. The experi- 

 ments were, therefore, carried out with larger quantities 

 of sugar in Erlenmeyer flasks. The following sugars were 

 tested : Dextrose, laevulose, maltose, saccharose, galactose, 

 and lactose, dissolved in neutral yeast water. In all these 

 solutions the species investigated grew equally well, and 

 proved that they were capable of assimilating those car- 

 bohydrates which they are unable to split up into alcohol 

 and carbon dioxide. All the species examined fermented 

 dextrose, Isevulose, saccharose, and galactose, and some of 

 them could also ferment maltose, but in other cases only small 

 quantities of alcohol were produced. Lactose was fermented 

 to an extremely small extent by two of the species. 



Van Hest found a small (4 to 5 ju) oval or almost round 

 Torula in top-fermentation Dutch beer, partly in the beer 

 returned, partly in beer in the lager casks, and again in the 

 fresh beer at the end of the primary fermentation. All these 

 were opalescent or turbid, and possessed a peculiar fruity 

 flavour. He termed the Torula, Sacch. pinophtorus melodus, 

 and found that under varying conditions its shape varies 

 greatly, and that a mycelium is found in the film. It is the 

 cause of the diseases of beer just described. In wort it brings 

 about a fairly , strong fermentation. Another Torula (S. 

 pinophtorus enervans) is often found in the same beer. It is 



