24 ELEMENTARY BACTERIOLOGY LABORATORY EXERCISES 
EXERCISE 38 
THE FERMENTATION OF CARBOHYDRATES 
The fermentation of carbohydrates, higher alcohols, and glucosides, with the 
production of acids (and gas in the case of some organisms) is a very valuable 
reaction in the study of bacteria. Since some organisms ferment a great many of 
these substances, while others ferment only a few, and still others do not ferment 
any of them, this reaction is frequently of great value in the differentiation and 
identification of bacteria. Most of the substances which have been used for study- 
ing the fermentation reactions of bacteria are given below. Some of these are 
only rarely used for this purpose, while others are frequently used. 
Inoculate glucose, lactose, and sucrose broths, contained in Durham tubes, 
with cultures of Streptococcus lactis, Bacterium coli, Bacillus subtilis and Proteus 
vulgaris. Incubate at 37° C. Observe after two days. 
The broth furnished contains brom cresol purple as an indicator of acid for- 
mation. 
CARBOHYDRATES 
Monosaccharids Disaccharids Trisaccharids Polysaccharids 
(Hexoses) (Hexosans) 
(C,H, ,0,) (C,,H,,0,,) (C,.H,,0,4) (C,H,,0,)0 
Glucose Maltose Raffinose Starch 
Fructose Sucrose Melicitose Inulin 
Galactose Lactose Dextrin 
Mannose Cellobiose Glycogen 
Sorbose Melibiose Galactan 
Cellulose 
(Pentoses) (Pentosans) 
(C,H,,0;) (C5H,O,)n 
Arabinose Araban 
Xylose Xylan 
Rhamnose (C,H,,0,) 
POLYHYDRIC GLUCOSIDES 
ALCOHOLS Salicin 
Mannitol Amyegdalin 
Glycerol 
Adonitol 
Dulcitol 
Sorbitol 
