PROTEOLYTIC ENZYMES OF SOIL FUNGI 513 



to amino-acids or to compounds containing amino nitrogen. 

 The action of the endoenzymes was stronger than that of the 

 exoenzymes, in the case of the fungi, but, in the case of the acti- 

 nomycetes, the reverse held true in most instances; this is prob- 

 ably due to the fact that the treated mycelium containing the 

 endoenzymes of the actinomycetes was added in much smaller 

 quantities than that of the fungi since the growth of the former 

 is very scant. It is interesting to note one thing in the 

 above table, namely that P. chrysogenum and Act. sp. 101, 

 which were found to produce more amino nitrogen than am- 

 monia when grown in a peptone solution (Waksman, 1918), 

 produced enzymes, which have a strong action upon the pro- 

 teins, while the other organisms, which produced more am- 

 monia than amino nitrogen in the peptone solution, gave rise to 

 much weaker enzymes; this fact may throw some light upon 

 the problem of protein decomposition by microorganisms. 



It was pointed out by Kendall and his associates (1915) that 

 the sugar content of the medium has a decided influence upon 

 the production of proteolytic enzymes by bacteria. To see 

 whether the same thing holds true with fungi, the enzymes ob- 

 tained from A. niger grown for fifteen days on the Peptone- 

 Czapek solution containing 0, 1, 3, 5 and 20 per cent of sugar 

 were used. 



It is seen from table 2 that the sugar content of the medium 

 ^as no decided influence upon the production of proteolytic 

 enzymes by A. niger. Where sugar was present in the original 

 medium just as much protein is split by both enzymes and, in 

 some cases, even more than by the enzymes of the organism 

 grown on the sugar free medium. The liquefaction of gelatin, 

 by the enzymes obtained from the above cultures did not appear 

 to be affected by the presence of sugar in the original medium. 

 The bacteria seem to behave differently from the fungi in this 

 respect. 



It was found advisable to determine first the proper reaction 

 which would be optimum for the activities of the enzymes and 

 also the proper age of the cultures, when the activities of the 

 exoenzymes would be at a maximum. Several organisms were 



