^2. Report of the Department of Bacteriology of the 



the nitrog-en is found in the form of paracasein monolactate dur- 

 ing the first week after the cheese is made. 



From the table on page 71 it is seen that in the breaking 

 down of \ gram of lactose about one-third of the nitro- 

 gen in the 25 grams of curd was changed into the monosalt. 

 This indicates that the breaking down, by bacteria, of sugar 

 amounting to more than two per ct. of the fresh curd is neces- 

 sary in order to account for the formation of the usual amount 

 of monosalt in cheese. 



result of too great formation of acid. 



Flasks containing 50 cc. of water and 25 grams of the same 

 cheese curd used in the preceding experiment were sterilized in 

 steam at 120° C. Each of a series of these flasks received i gram 

 of sterile lactose and was inoculated with the same culture of lactic- 

 acid bacteria which had been used in the preceding experiment. 

 Additional sterile flasks received i cc, 1.5 cc, and 2 cc. of chemi- 

 cally pure lactic acid but were not inoculated with bacteria. Bac- 

 teriological examinations made in connection with each analysis 

 showed that the lactose series contained but the single species of 

 bacteria with which it had been inoculated while the sterile flasks 

 to which acid had been added remained sterile. The amount of 

 nitrogen insoluble in water but soluble in a 5 per ct. solution of 

 sodium chloride at the end of various intervals expressed in per- 

 cents of the total nitrogen is given in the following table. 



Table III. — Paracasein Monolactate Formed in Cheese Curd by Bacteria 



AND BY Acid. 



Date. 



February 2i — Initial 



March 10 



March 24 



May 22 



August 15 . . 



Lactic-acid 

 bacteria 



I gm. lactose. 



Per ct. 



4-34 



2331 

 20.60 



9.76 



7-32 



3-52 

 325 



3-25 

 3-52 



Sterile Hasks and chemically pure 

 lactic acid 



Pt-y ct. 

 3-90 

 4-34 



2.17 

 2.93 



Per ct. 

 3-90 

 4 34 



1.62 

 2. 16 



Per ct. 

 3-90 



4-34 



1-95 



