Feb. 15, 1921 



Amylase of Rhizopus tritici 



779 



solution had a much less inhibitory effect on the production of amylase 

 with A. niger than with P. glaucum. Similar conclusions were reached 

 by Duclaux (10) with P. glaucum and A. glaucus, though he considered 

 only the enzyms which diffused into the culture medium. The investi- 

 gations of Kylin (20) with P. glaucum, P. biforme, and A . niger corrob- 

 orate in a general way the results of other investigators. He found no 

 qualitative regulation of the enzyms studied by him (diastase, invertase, 

 and maltase), though a quantitative regulation was conclusively proved. 

 With P. glaucum the regulating secretion of diastase was greater than 

 with A. niger. Knudson (19), on the other hand, demonstrated a quali- 

 tative regulation of tannase with A. niger and P. sp. These fungi pro- 

 duced gallic acid by the fermentation of tannic acid when the latter 

 was added to a modified Czapek's nutrient solution, but if supplemented 

 with sucrose no tannase was formed. A number of other substances as 

 a source of carbon likewise failed to stimulate the secretion of tannase. 

 Young (28) studied the inulase formation by A . niger in a nutrient solu- 

 tion and found a well-marked quantitative regulation of the production 

 of the enzym. He showed that inulase was produced in greatest amount 

 in the mycelium (extracellular enzyms not studied) when inulin was 

 used as the source of carbon but was likewise produced when other car- 

 bohydrates were employed. The substances most closely allied to inulin 

 were most efficient in the production of the enzym. 



The results of the writer's experiments which follow demonstrate also 

 a quantitative regulation of amylase in nutrient solutions. Sweet 

 potato bouillon and Czapek's modified nutrient solution (see p. 762) 

 with glucose and starch in combination or alone in varying amounts were 

 used as substrates. 



In all these experiments the fungus was grown in 2 -liter flasks contain- 

 ing 1,000 cc. of solution. At the end of the growth period the mycelium 

 was removed and prepared in the usual way, according to the "aceton- 

 dauerhefe" method of Albert and Buchner, the mycelium from the flasks 

 of each series being mixed together to make a compound sample. 



Experiment i . — The fungus was grown on Czapek's modified nutrient 

 solution with glucose or starch or both as a source of carbon. The 

 cultuies were incubated for 8 days at 32 ° C. Hydrolysis of starch was 

 carried out for 19 hours at 32 by using 0.25 gm. of enzym powder in 50 

 cc. of a 0.5 per cent starch paste solution. (Table XIII.) 



Table XIII. — Source of carbon in Czapek's modified nutrient solution and amount of 

 hydrolysis by the enzym powder per 10 cc. of the substrate 



25120°— 21- 



