Lewis Knudson 



177 



The transformation of salicin or arbutin was inhibited in the pres- 

 ence of certain amounts of glucose, cane sugar or starch. Like- 

 wise Katz'* found that Penicillium glaucum did not secrete the 

 enzyme diastase when, along with 0.25 per cent soluble starch, either 

 2 per cent glucose or 15 per cent cane sugar was offered. Asper- 

 gillus niger was not influenced noticeably in the secretion of the 

 tannase by the presence of the 10 per cent cane sugar, while the 

 Penicillium sp. was markedly influenced. 



Another noteworthy fact in regard to the Penicillium sp. is the 

 small increase of gallic acid between the twentieth and thirty-fifth 

 day. It seems that the enzyme secreted was so very little, or of 

 such feeble activity or destroyed, that a very limited transforma- 

 tion only was effected. Even at the end of fifty-six days the tannic 

 acid was not entirely converted, and the increase of gallic acid after 

 the end of thirty-five days was relatively small. 



Influence of concentration of sugar on growth. For an explana- 

 tion of the protective action of 10 per cent sugar the following table 

 is suggestive. Each result is the average of sixteen cultures of 

 Aspergillus niger. 



TABLE VIII. 



CULTURE 

 NO. 



COMPOSITION OF NUTRIENT SOLUTION 



Check: 50 cc. sol. A + trace Fe2Cl 



+ 2.5 gms. sugar 



50 CO. sol. A + trace FejCls 



+ 8.55 gms. sugar 



50 cc. sol. A + trace FejCls 



+ 17.1 gms. sugar 



50 cc. sol. A + trace FejCls 



+ 25.65 gms. sugar 



50 cc. sol. A + trace FeaCIa 



+ 37.00 gms. sugar 



50 cc. sol. A + trace Fe-zCli 



+ 42.50 gms. sugar 



SUGAR 



IN CULTURE 



SOLUTION 



per cent 



17.1 



34.2 



51.3 



74.0 



85.0 



DRY WEIGHT 

 OF FUNGUS 



' 0.779 

 1.239 

 1.513 

 1,590 

 1.308 

 1.230 



The table shows that the optimum sugar content is above 5 

 per cent. It is possible that the increased growth in the culture 

 solution of over 10 per cent sugar is produced not by an assimi- 



3< J. Katz: Die rggulatorische Bildung von Diastase durch Pilze, Jahrh- 

 f. wiss. BoL, xxxi, pp. 599-618, 1898. 



