1 66 



Tannic Acid Fermentation 



V. COMPARISON OF ORGANISMS AND INFLUENCE OF TIME AND 

 GROWTH ON FERMENTATION. 



Comparison of organisms. Employing an infusion of gall nuts 

 containing 10.5 per cent tannic acid, VanTieghem^^ found that the 

 fermentation was completed by Aspergillus niger in six days and 

 by Penicillium glaucum in eight days, when the temperature of 

 incubation was 35° and the supply of oxygen was limited by keep- 

 ing the flask stoppered. In the weaker concentrations, Penicillium 

 glaucum fermented the tannic acid more vigorously. Since in 

 VanTieghem's experiments the temperature was rather high and 

 the conditions of growth approached anaerobic conditions, it was 

 believed that a better comparison could be made by supplying the 

 optimum conditions for the growth of each. In all the natural 

 fermentations (in unsterilized solution) of the tannic acid, Asper- 

 gillus niger always developed first and then Penicillium sp. 

 So marked is this succession that by exposing a nutrient solution 

 of 10 per cent tannic acid to the air a pure culture of Aspergillus 

 niger may usually be obtained. This suggests that Aspergillus 

 niger may possess the greater fermentative capacity, but an experi- 

 ment was required. 



In the first experiment solution A and tannic acid were used, 60 cc. of the 

 solution being placed in Erlenmeyer flasks of 150 cc. capacity. The flasks 

 were sterilized for forty-five minutes at 115°, inoculated, and kept for two 

 we^cs at a temperature of from 18°-28°, the average being close to 24°. 

 The felts were then removed, thoroughly washed, and the wash water added 

 to the culture solution, the solution being then brought up to 500 cc. volume 

 and analyzed according to Dreaper's^' method. The figures below are for 

 Aspergillus niger, the averages of six cultures, while for Penicillium sp7\ 

 the averages of five cultures are given. 



TABLE I. 



" Loc. cit. 

 2' Loc. cit. 



