232 



curve was found in ail my expenments, both for the culture so- 

 lution as for the mycélium, no matter what the concentration of 

 the diastase was. The amylase of Aspergillus niger seems to be 

 mfluenced very slightly by the degree of acidity i. e. the optimal 

 acidity for the enzyme has very wide limits. It is fortunate, that 

 the fungus itself keeps the acid concentration of the culture so- 

 lution optimal, so that we do not need to acidity the liquids arti- 

 ficially^. Sometimes even the acidity may be too high, but then 

 during the expenment the liquid is mixed with neutral slarch so- 

 lution and by this means the P^ is again brought down to the 

 optimum. 



In the above expenment great accuracy was imperative. From 

 fig. 1 it can be seen that this is possible by using lodine as an in- 

 dicator. I may also mention that there is a close agreement between 

 my results and those of Adler on the influence of the culture mé- 

 dium on the diastase of malt. 



It is clear therefore that in this expenment I need only ccnsider 

 the acidity in the following case. From the curve we see, that 

 Ph =^ 6 is already less than optimal, at Pjq = 7 the action is 

 almost zéro. The mycélium itself contains hardly any acid. When 

 extracted with water, the solution has a P^ of + = 6 and this 



^ It is not selfevident at ail that llic fungus shouid produce tl\e optimum hy- 

 drogen ion concentration itself. This can be seen from an investigation I made on 

 the diastase concentration of cuhures of Monilia sifophila. Thèse cultures were 

 three weeks old and were grown on 5% lactose. 1 he culture solution had a 

 Ph ^ = 8, and the hydrolysis of starch proceeded very slowly. When however 

 the degree of acldity was artilicially increased, hydrolysis was niuch faster. The 

 follcvang results were obfained 



Ph =^ 3.95 hydrolysis m 52 minutes 



5.40 31 



5.90 32 



± 6.50 36 



X 7.50 (natural slate) 500 



This resuit is only a preliminary investigation, but it shows that in ail thèse expe- 

 riments v\e shouid be carfful to kncw the optimum Ph 3* which the enzyme must 

 be observed. 



