DissoivViN& e;nzyme;s. 



85 



similar results as did also 5 per cent solutions of precipitates from beef broth cultures 3, 6, 9 and 17 

 days old. 



Temperature. — The optimum temperature for most rapid growth of B. carotovorus is 28° C. to 

 30° C. Contrary to expectations, however, enzym production is not the most active at this tempera- 

 ture. The enzym content of broth cultures grown for 8 days at room temperatures (18° to 22° C.) 

 was greater than that of similar cultures grown the same length of time at 30° C. 



The activity of the enzym with respect to the following environmental conditions was also 

 determined : 



Effect of Long Keeping. — In the author's opinion there was no loss of enzymic activity in dried 

 enzym-containing precipitate kept for months or even years. 



Relation of Temperature to Activity. — Solutions of the alcoholic precipitate from carrot broth 

 cultures were tested on carrot sections at different temperatures. Action slight at 2° C, good at 

 22°, better at 32°, best at about 42°, inhibited somewhat at 48°, pronounced inhibition at 50°, prac- 

 tically complete inhibition at 5 1° and above. The optimum lay between 40° and 45° C. Such solu- 

 tions were uninjured by an hour at 49° C. either in the presence or absence of carrot tissues, but 

 practically destroyed by exposure to 51° for 10 minutes. 



Comparative studies show that the points of inhibition and destruction were approximately 

 ID degrees lower in the solutions of the precipitate than in the original broth. 



In studying the effects of acids and alkalies the alcoholic precipitate obtained from carrot 

 broth cultures was used. The strength of the acid and alkali solutions was determined by titration 

 with phenolphthalein. 



Alkali. — The presence of sodium hydroxide, titrating — 2 per cent, inhibited the reaction slightly. 

 When sufficient alkali was added to make the liquid titrate — 10 per cent, inhibition was total. 



Acids. — (These acids were made up by weight and titrations of strength determined afterward). — 

 A very small amount of hydrochloric acid seemed favorable to the action of the enzym, a reaction 

 of + o. 5 per cent being about the optimum. There was great inhibition when the reaction was + 2 

 per cent and at +5 it was practically complete. 



Various organic acids were tested, the results in detail as given by the author are shown in the 

 following table : 



"From these results it will be seen that these organic acids in no case aided the action; that 

 where the acidity, as shown by titration, was -fo.5 per cent and less they were practically without 

 effect" that +1.0 per cent and above distinctly inhibited in all cases where it was tried, and that from 

 -j-5 per cent to +10 per cent led to complete inhibition." 



Effect of Plant Juices. — Some experiments were carried on to determine whether the normally 

 acid cell sap has a similar effect on the. enzym. To the expressed juice of carrot, radish, and ripe 

 tomato were added equal parts of a 5 per cent aqueous solution of the precipitated enzym from a 

 carrot broth culture. There was a slight diminution in the rate of action as compared with solutions 

 in distilled water. This was a little more pronouncedin the case of the tomato. The test was repeated 



