Lewis Knudson 173 



the latter the tannic acid was completely transformed. The differ- 

 ence in the amount of tannic acid transformed was not sufficient, 

 however, to account for the loss of gaUic acid in the synthetic solu- 

 tion and the marked increase in the infusion culture. Despite the 

 greater weight of the fungus this increase of gallic acid was more 

 in the infusion culture. A similar condition existed at the end of 

 six days. The explanation of this point seems to be found in the 

 fact that the infusion cultures contain various organic compounds 

 which are utilized in place of the gallic acid; that is, elected in 

 preference. At the end of four days probably none of the gallic 

 acid has been assimilated. The subsequent decrease in gallic 

 acid was due to its use after the exhaustion of more favorable 

 organic nutrients. After the sixth day in the infusion culture there 

 was no further growth of the organisms and no decrease in the gallic 

 acid. The growth was less than one-half of that in the synthetic 

 cultures, probably due to the lack of inorganic nutrients, although 

 the presence of injurious metabolic products might also have been 

 a factor, as the organic food supply was by no means exhausted. 

 The conditions which obtained for the Aspergillus niger cultures 

 apply also to those of Penidlliuni sp. 



Another point of interest brought out by the comparison is 

 the more rapid fermentation in the infusion than in the synthetic 

 solution. In the Aspergillus cultures the tannic acid was com- 

 pletely transformed in the gall nut infusion by the eighth day, when 

 the weight of the fungus was 0.262 gram. In the synthetic cul- 

 tures transformation was not complete by the sixteenth day, when 

 the weight of dry mycelium was 0.513 gram. In the Penicillium 

 cultures, also, the results are comparable. 



In another experiment in which a gall nut infusion was used 

 containing 2.04 grams of tannic acid and 0.56 gram of gaUic acid 

 per 50 cc, at room temperature, there was maintained for thirty 

 days an increase of gallic acid. Practically all of the fermentation 

 occurred before the eleventh day, and the gallic acid was protected 

 by the other organic substances. 



Since the experiments with the infusion cultures indicated that 

 the gallic acid was protected to a certain extent by the election 

 of other organic substances, it was determined to try the addition 

 of sugar to the culture solution with respect to its effect on the 

 election of foods and hence on the yield of gallic acid. 



