442 STATE BOARD OF AGRICULTURE. 



Expt. VII. 



Comparison of the Action of Pepsin, of Rennet, and of the Red Yeast 



upon Weak Ixictic Bacteria. 



In Expt. IV, it is especially noted that an enzyme is found in the 

 germ-free filtrate of the yeast LZ which is identical in its action upon 

 heated milk with that of rennet; in the mixed culture, a casein-digest- 

 ing enzyme is also present. As rennin hardly ever exists wholly free 

 from pepsin and this latter enzyme is proteolytic in action, the assump- 

 tion was made that this latter ferment is a pepsin-like body. 



For comparison with the action of these enzymes produced by the 

 3'east, a germ-free filtrate each of commercial rennet extract and pepsin 

 solution was substituted for the filtrate of the yeast. 



The rennet used was an extract put up by the Marshall Dairy Lab- 

 oratory, Afadison, Wisconsin, and the label stated that it was preserved 

 by the addition of 1% boric acid. Merck's pepsin, powdered form, was 

 used in the proportion of 1 g. to 100 cc. distilled water for the pepsin 

 solution. 



Over 100 cc. of each solution was filtered through a sterilized asbestos 

 Gooch filter iuto a sterile Bunsen filter flask. This filtrate in each case 

 was bacteria-free. Under sterile jjrecautions each filtrate was trans- 

 ferred in about equal proportions to two sterile flasks, one of these 

 boiled for about 5 minutes over a free flame, the other left unheated. 



The experiment tabulated under Table XX was duplicated with the 

 heated and unheated rennet and pepsin filtrates. One-tenth cubic cen- 

 timeter of a 10 day old culture of Stock lactic (not curded) was used 

 in carrying on these two experiments. In addition to the methods 

 stated in Expt. Ill, 10 cc. of unheated rennet and pepsin filtrates were 

 each added to a flask of sterile miik, as checks. 



