May i6 p 1921 
Respiration of Sweet Potato Storage-Rot Fungi 
221 
These variations are more or less dependent upon the temperature at 
which they are carried out and the length of time the experiment has run. 
DISCUSSION OF RESULTS 
PRODUCTS OF FERMENTATION 
Alcohol. —It is well known that fungi often produce alcohol and 
various organic acids as fermentation products during respiration. If 
the oxidation of the sugar was complete, C 0 2 and water only would be 
produced, but results obtained by various workers have shown that other 
substances are often formed. An extensive literature is extant on the 
production of alcohol by different fungi in culture, but no attempt will 
be made to review all or any considerable part of it. Suffice it to say 
that the results of Brefeld (2), Fitz (7), and Hansen (<?) with different 
species of Mucors, Aspergillus, Rhizopus, and Penicillium, and more 
recenty Kostytschew (12) with Aspergillus niger show that alcohol pro¬ 
duction by fungi is not uncommon. The amount of alcohol produced 
by the different organisms, according to the authors cited, differs with 
the medium used, the temperature, and the length of time the organism 
was grown. Mucor racemosus was found by Hansen to produce as 
much as 7 per cent by volume in 12 months at room temperature, and 
Fitz showed that M. mucedo Bref. would form 0.8 per cent alcohol by 
weight in 7 weeks at a temperature of 30°C. 
Obviously it is not possible to determine with any degree of accuracy 
by present chemical methods just what a fungus does in a solution as 
complex as Czapek’s nutrient medium. The writers' experiments 
showed that alcohol was produced to a limited extent by four of the 
fungi studied—namely, Fusarium acuminatum, Rhizopus tritici, Diplodia 
tubericola , and Mucor racemosus . R. nigricans and M. racemosus were 
shown to be alcohol producers by other investigators, the former to a 
very limited extent, and the latter in considerable quantity. So far as 
the writers are aware, no one has reported the production of alcohol by 
F. acuminatum, R. tritici, or D. tubericola. If alcohol was produced by 
the other fungi it was either utilized by the fungus or formed in such a 
limited amount that it could not be detected by the method employed. 
The results from which the conclusions were drawn, although not un¬ 
qualified proof, were determined by the following method: One hundred 
cubic centimeters of the solution were neutralized with magnesium car¬ 
bonate (MgCOg). Fifty cubic centimeters were then distilled off, and 
from this a 25-cc. fraction was taken. The iodoform test was applied 
to the last distillate. A positive test was obtained in most cases only 
dpon warming. The second distillate in all cases, when the iodoform 
test indicated the presence of alcohol, had a lower specific gravity than 
water. The same tests were carried out with the control solutions with 
negative results. 
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