Feb. is, 19*1 Amylase of Rhizopus tritici 775 



at first, a felt forming later on the surface of the liquid. The solutions 

 were tested for reducing sugars at the beginning of the experiments, 

 but in no case were any found. The fungus must then of necessity have 

 either to utilize the starch directly or first have converted it into some 

 simpler form. From time to time some of the liquid was drawn off, 

 and the reducing sugars were determined. The results showed an 

 increasing amount of reducing sugars present with each subsequent 

 determination, from which it is evident that the fungus hydrolyzed the 

 starch in excess of its needs. If the growth continued long enough the 

 solution which was milky in color at first finally became clear, showing 

 that practically all the starch was hydrolyzed. Many experiments in 

 the course of these investigations likewise demonstrated clearly that the 

 fungus hydrolyzed the starch in the solution, although reducing sugars 

 were already present. Furthermore, the hydrolysis of the starch in a 

 solution of starch and glucose began very soon after inoculation, which 

 suggests that the enzym diffuses into the solution soon after the begin- 

 ning of growth. This subject will receive further consideration in the 

 discussion of an extracellular enzym. 



EXTRACELLULAR ENZYM 



The results in the following experiments show other interesting facts 

 in addition to the production of an extracellular amylase. Two nutrient 

 solutions a and b, differing in the source of nitrogen, were used. Solution 

 a had the following composition : 



Water 1, 000. 00 cc. 



Magnesium sulphate (crystallized) ^ .50 gm 



Potassium acid phosphate 1. 00 gm 



Potassium chlorid .50 gm 



Ferrous sulphate .01 gm 



Sodium nitrate 2. 00 gm 



Starch 10. 00 gm 



Solution b differed from a in that the sodium nitrate was replaced by 

 5 gm. of ammonium nitrate. 



The chemicals were first dissolved in the water by steaming, after 

 which the starch was added and the entire mixture was sterilized by 

 autoclaving. 



The growth in these two solutions was remarkably different. In a 

 the mycelium was mostly submerged, while in b a thick felt was formed 

 on the surface. Solution a produced in 16 days of growth a total dry 

 weight of 0.0298 gm. ; b, 0.7198 gm., or about 24 times as much. Both 

 solutions were inoculated on October 27. The reducing sugars and 

 starches were determined at stated intervals thereafter, as shown in 

 Table XI. 



