INULASE FORMATION IN ASPERGILLUS 127 



however, that the conditions under which the fungus was grown 

 were extremely hmited, since only the common carbohydrates 

 were used as a source of carbon. It is not at all improbable that 

 the use of proteins, organic acids, alcohols, etc., as the source of 

 carbon might give entirely different results and, at least, it is to 

 be expected that some of these substances would be less efficient 

 in stimulating inulase formation than were any of the substances 

 employed in this work. The results of Went (1901) in his studies 

 of invertase and of Kylin with maltase, etc., render it highly im- 

 probable, that any qualitative regulation of inulase formation 

 could be found. These investigators employ a great variety of 

 substances including peptone, organic acids and polyhydric al- 

 cohols as the source of carbon and find that the enzymes men- 

 tioned are secreted under all conditions. 



The quantitative regulation of enzymes has been long known 

 and is a firmly established fact so far as the fungi are concerned. 

 It seems to be quite generally the case that the amount of any 

 enzyme produced may vary widely according to the environ- 

 ment of the fungus. Certain investigators have found that en- 

 zyme formation can be greatly inhibited by growing the fun- 

 gus at low temperatures. Kostyschew (1907) and others have 

 shown that appreciable amounts of a zymase-like enzyme are 

 produced by certain fungi and the work of Junitzky (1907) 

 shows that in this case there is an increased enzyme production 

 due to lack of oxygen, since his results show that these fungi 

 produce this same enzyme in small amounts under ordinary 

 conditions. 



It has been shown by several investigators that the effect of 

 certain inorganic salts is to increase or decrease enzyme produc- 

 tion. As mentioned before Herissey (1899) finds that the pres- 

 ence of large amounts of ammonium nitrate in the culture 

 medium entirely inhibits the formation of emulsin in certain 

 fungi. In the light of the more recent work on enzyme regula- 

 tion, it seems more than likely that emulsin formation is not 

 entirely suppressed in this case. It seems possible from the 

 results of several French investigators, that the stimulating ef- 

 fects of such a substance as zinc, may perhaps be related to its 

 effect on enzyme production. 



