26 BULLETIN 782, U. S. DEPARTMENT OF AGRICULTURE, 
The results of the study of the fermentation of the organic-acid 
salts indicate that some of the bacteria could obtain their carbon 
from the methyl, alcohol, or aldehyd (as in formic acid) radical of 
the salts of organic acids but not from the carboxyl group. Carbon 
was most easily obtained from the methyl group, as is shown from 
Table 11, where it is seen that most of the cultures were able to obtain 
their carbon from acids which had no alcohol radical, such as succinic 
or acetic. They were able to obtain it to about the same extent 
from citric, malic, and lactic acids, which contained both the methyl 
and alcohol radicals. In this case it is believed that the methyl 
radical supplies the carbon, since acids containing merely the alcohol 
radicals were not readily fermented. Only a small number of the 
cultures utilized the carbon from the alcohol radical where it was 
linked with a carboxyl and another alcohol radical, as in mucic, 
tartaric, and glyceric acid. The carbon did not seem to be utilized 
from an alcohol radical linked only to a carboxyl radical, as in 
glycolic acid. Pyruvic acid was easily fermented by all the cultures, 
and in this case the carbon may come from either the methyl or 
ketone radical. A. Fischer mentions in his book "The Structure and 
Functions of Bacteria," published in 1897, that bacteria are able 
to utilize carbon from the methyl radical more readily than from the 
alcohol radicals and they are unable to utilize the carbon from the 
carboxyl radical, as in oxalic acid. Our results confirm his opinion 
in the matter. 
When the salts of organic acids were fermented an alkaline reaction 
was produced in most cases, the exceptions being butyric, valeric, 
and caproic acids. In the case of these acids the fermentation may 
proceed in one of two ways: Either the methyl radicals may be 
oxidized until a carbonate is produced and the medium becomes 
alkaline, or the acid may be split into other acids containing fewer 
carbon atoms. For example butyric may be oxidized as follows: 
CH 3 CH 2 CH 2 COOH+0 2 =2 CH 3 COOH 
butyric acetic 
CH 3 CH 2 CH 2 COOH+0 2 =HCOOH+CH 3 CH 2 COOH 
butyric formic propionic 
The oxidation of butyric acid to other acids may account for the 
increased hydrogen-ion concentration produced by certain alkali 
bacteria, since under ordinary conditions this concentration is lowered 
by the production of carbonates. Both these forms of fermentation 
may take place at the same time, but in the great majority of cases 
one or the other predominated, as is shown in Table 10. While 
many of the cultures produced an acid reaction in n-butyric and 
n-valeric acids, all those which fermented isobutyric, a or oxy- 
butyria and isovaleric acids produced an alkaline reaction. 
