Lewis Knudson 171 



cillium cultures only 70 per cent was converted in the same time. 

 Not only does Aspergillus niger produce a more rapid fermenta- 

 tion, but also a greater production of gallic acid is effected; for, 

 as indicated, the maximum yield of gallic acid in the Aspergillus 

 cultures is twice that in -the Penicillium cultures, and this in spite 

 of the fact that a greater weight of Aspergillus niger is produced. 

 Furthermore, in the Penicillium cultures there occurs a decrease 

 of the gallic acid even when considerable tannic acid is still present 

 in the culture solution. 



In order to understand these differences between Aspergillus 

 niger and Penicillium sp., the composition of the infusion must 

 first be considered and an idea of this may be obtained from con- 

 stituents of the gall nuts. In addition to tannic acid, the gall 

 nuts contain (Guibert'") galUc acid, chlorophyll, starch, gums, 

 sugar, proteins and various inorganic salts and other compounds. 

 A water extract of the gall nuts would contain in solution and 

 suspension a certain amount of most of these substances, and the 

 subsequent sterilization would probably result in transformations 

 which would make certain of the organic compounds more avail- 

 able. 



Aspergillus niger is an omnivorous organism in its relation to 

 the utilization of carbon compounds. The growth of this organism 

 for the first few days is probably at the expense of the other organic 

 substances present, and the gallic acid, in this case, accumulates. 

 All the facts indicate that while Aspergillus niger is utilizing the 

 organic compounds other than tannic acid, it secretes the enzjTne 

 tannase (this point will be further developed in a separate paper), 

 and consequently the transformation of the tannic acid goes on, 

 and galhc acid accumulates. When the other organic compounds 

 are exhausted, the gallic acid is utiUzed, and then the decrease 

 begins. As shown previously, Penicillium sp. tends to utilize the 

 gallic acid before it transforms the tannic acid, for gallic acid is a 

 favorable nutrient carbon compound for this organism. Further- 

 more, as I will show in a later paper, the presence of the other or- 

 ganic compounds may decrease the secretion of the enzyme tan- 

 nase by Penicillium sp.; and since the utilization of the gallic acid 

 exceeds the formation of this substance, there results a decrease 



'" Quoted from H. Trimble: loc. cit. 



