88 UNIVERSITY OF WISCONSIN STUDIES 
The fermentation of carbohydrates and alcohols—In con- 
sidering the ability of these cultures to utilize different sources 
of carbon some consideration must be given to the difficulty 
sometimes encountered in determining if a fermentation has 
actually taken place. With the ordinary culture and most 
of the sugars and alcohols there is no difficulty in determining 
fermentation either by the gas formation, the change in 
titratable acidity, or in hydrogen ion concentration. With 
some cultures the reaction is obscured by a weak evolution of 
gas or a rapid reversion of the reaction. 
Gelotin - $82 =106 and P- Gelatin - 524215 -3.0 Vand Pr 
400 80 60 40 20 +#[- 20 40 60 80 00 100 80 60 40 20 +|- 20 40 60 80 100% 
Indol. es 
Saccharose, 
Roffinose. 
Starch. 
Inutin. Leal bd ree eee eee Bee [eee (| 
Mannitol. pats acti ee een! Serer Palle 
Glycerol, a [ka ‘ae ee eed peed ee ee 
Salicin. bi iS - 
Dutcitol. erated 
Adonito/. vend cnet tarebfeciedl feos Eee) eee ee | a 
L N 
Fig. 2 
In most of the sugars the change in reaction is rapid and 
distinct but in some of the alcohols, notably glycerol, the 
fermentation is so slow that it may be in doubt for many 
days. We have considered an evolution of gas in the absence 
of any apparent change in acidity or an appreciable change 
in acidity without evident gas formation as fermentations. 
Figure 2 shows that while there is no perfect correlation, 
there is a distinct difference in the fermentative ability of the 
two groups. The cultures of the high ratio group almost 
without exception ferment saccharose and raffinose while only 
about 40 per cent of the low ratio group utilize these sugars. 
Starch is also utilized much more commonly by the high ratio 
cultures. On the other hand, more of the low ratio cultures 
ferment the aleohols mannitol, glycerol and duleitol than is 
the case with the high ratio group. This does not hold for 
adonitol which seems to be more available for the high ratio 
type. he percentage of cultures fermenting the glucoside 
