Feb. is, 1921 



Amylase of Rhizopus tritici 



765 



EXPERIMENTAL DATA 



HYDROLYSIS OF RAW STARCH 



Preliminary experiments showed that Rhizopus tritici produced an 

 enzym which hydrolyzed starch to reducing sugars. This fungus is com- 

 monly found as a cause of the decay of sweet potatoes in storage and 

 along with R. nigricans probably is responsible for the greater percentage 

 of decay attributed to the Mucoraceae. In just what form they utilize 

 carbohydrates when growing on the sweet potato is not known, but 

 that they are responsible for certain carbohydrate changes in the host 

 directly through their own activity or by stimulating the host to do so, 

 or both, will be shown by investigations now under way. 



Most of the previous work with amylase secreted by fungi was carried 

 out with starch paste or soluble starch. This obviously is not the form 

 in which it occurs in the host, and although the enzym might digest 

 starch paste, it is not safe to conclude that it would act on raw starch, or 

 if at all, to the same degree. 



Ward (24) concluded from the appearances of the starch grains of the 

 Irish potato that they were not acted on by Pythium, while Hawkins and 

 Harvey (14), on the other hand, found from a chemical determination of 

 the total starch present in the sound and rotted portions of the same 

 potato that the starch content was actually lower in the latter than 

 in the former. That all fungi do not behave the same as regards their 

 action on starch is evident from the fact that Hawkins (/j) found that 

 neither Fusarium oxysporum nor F. radicicola apparently alters the 

 starch content of Irish potato. It is evident from the results of the 

 authors just cited that no general conclusions can be drawn for all fungi 

 from the behavior of any one or more fungi. The first experiments, 

 therefore, were designed to test the comparative hydrolysis of raw starch 

 and starch paste. The results are given in Table II. 



Table II. — Results of hydrolysis of raw starch expressed in terms of reducing sugar {aver- 

 age of several tests) 



<* Starch macerated in sand before hydrolysis was started. 



