Lewis Knudson 



199 



then inoculated. The growth in gallic acid was rapid, but not 

 eavy In the solutions in which the glucosides were present, 

 growth was at first very slow, but after the transformation of the 

 glucosides had begun, growth was rapid. While it required eight 

 days to develop the first felts in the two glucoside solutions, the 

 second felts (after the removal of the first) developed in two days. 

 The felts first formed were removed and treated according to the 

 methods previously described, and the powdered mycelium then 

 added to 100 cc. of a 0.90 per cent solution of tannic acid which 

 contained also 2 per cent of toluene. After incubating two days 

 at 40°C. , the solutions were analyzed for galUc acid. The composi- 

 tion of the nutrient solutions and the gaUic acid formed by the 

 powdered mycelium are given in table IX. 



TABLE IX. 

 Aspergillus niger. 



The control contained 0.327 gram gallic acid and 0.555 gram 

 tannic acid. 



In preceding tables it has been seen that gallic acid at certain 

 concentration in the presence of 10 per cent sugar does not stimu- 

 late the formation of the enzyme tannase. When gallic acid is 

 present alone as the source of carbon, the enzyme is produced. 

 If tannic acid is a glucoside, it might be expected that the presence 

 of another glucoside would stimulate the production of some tan- 

 nase, but such was not the case. Nevertheless, glucosides were 

 transformed by the organism. While the gallic acid stimulates the 

 formation of the enzyme tannase, it does not do so as effectively 

 as the tannic acid. 



VI. EFFECT OF CONCENTRATION OF GALLIC ACID ON PRODUCTION OF 



TANNASE. 



Since the amount of tannase produced is regulated by the relative 

 concentrations of sugar and tannic acid it was deemed important 

 to determine if the amount of the tannase produced could be in- 



