June 9, 1923 
Substrate and Hydrogen-Ion Concentration 
863 
The original Pfeffer's and Richard's solutions call for cane sugar, but, 
in view of the fact that the fungus used in these investigations does not 
utilize it, glucose was employed instead. All the different media were 
prepared in large quantities and held in flasks stoppered with cotton and 
covered with oiled paper until ready for use. Just previous to using, 
30 cc. of the solutions were pipetted into each of fifteen 100 cc. Erlen- 
meyer flasks which were then autoclaved for 20 minutes at 15 pounds 
pressure. Ten flasks of each solution (set) were inoculated after which 
they were incubated at 35° C. The remaining 5 flasks of each set were 
held as controls. 
At the end of the growth period, usually three to four days, the myce¬ 
lium from all the flasks of a single series was collected into one compound 
sample and prepared for macerating experiments, according to methods 
previously described. The solutions on which the fungus grew in each 
set were made into one compound sample and equal portions (about 
30 cc.) pipetted into small flasks to which raw sweet-potato and carrot 
disks were added. A portion of each of the solutions was steamed for 
10 minutes to inactivate the enzym which, together with flasks of the 
original solutions which had not supported a fungous growth, were 
used as controls. An accurately weighed amount of mycelium (0.25 
gm.) ground in pure quartz sand was used in determining the macerat¬ 
ing action of the hyphae. The mycelium was not extracted in water 
prior to the addition of the raw disks, since previous experiments showed 
(9) that the rate of maceration was not influenced thereby. The ground 
mycelium was included in the system. 
The hydrogen-ion concentrations of the solutions and of the controls 
(not inoculated) were determined by the electrometric method as rapidly 
as possible after the hyphae were removed, in all cases during the same 
day. 
EXPERIMENTAL DATA 
In this series of experiments 10 different solutions were employed, 6 
being of vegetable origin, 3 synthetic solutions, and i of beef bouil¬ 
lon. In one or two series of experiments in which a modified Czapek’s 
nutrient solution was employed as a substrate it v/as noted that no pec- 
tinase seemed to be produced, although it was abundantly secreted in 
sweet-potato decoction with which it was being compared. It was also 
noted in these cases that even in the absence of pectinase a certain 
amount of maceration of sweet-potato disks occurred. In view of these 
facts, experiments were undertaken to study the regulating action of 
certain substrates on the production of the enzym. The substrates here 
employed were selected as being representative of the vegetable decoc¬ 
tions and synthetic solutions in common use. It was also believed that 
if the substrate exercised any influence on the production of pectinase 
that fact would be brought out by these media. 
MYCELIAL GROWTH 
In these series of experiments the dry weight of the mycelium was not 
determined. The mycelium was all used in maceration experiments. 
In general, the growth and fruiting of the fungus on the media of vege¬ 
table origin were good, being much better than they were when the fun¬ 
gus was grown on the synthetic solutions or on beef bouillon. Bean, 
carrot, and turnip decoction yielded the best growth and fruiting. A 
fair growth took place in prune decoction, but little or no fruiting. The 
