BULLETIN No. 167 JANUARY, 1916 



MASSACHUSETTS 

 AGRICILTLRAL EXPERIMENT STATION 



I 



THE RELATION OF HYDROGEN ION CONCENTRATION OF 



MEDIA TO THE PROTEOLYTIC ACTIVITY 



OF BACILLUS SIBTILIS 



II 



PROTEOLYSIS OF STREPT. ERYSIPELATIS AND STREPT. 



LACTICIS COMPARED INDER DIFFERENT 



HYDROGEN ION CONCENTRATION 



By ARAO ITANO 

 Department of Microbiology, Massachusetts Agricultural College 



This publication involves two parts, as follows: 



Part I. — This investigation has been undertaken to determine 

 the bacteriological value of Sorensen's method for the study of 

 proteolysis in conjunction with hydrogen ion concentration. In 

 its execution it has been thought wise to select the well-known 

 organism, B. subtilis, which enables ready interpretation. The 

 investigation shows that certain hydrogen ion concentrations 

 measure the exact influence both inhibitory and prohibitory, and 

 indicate the exact limits of the proteolytic activity of B. subtilis. 

 It shows, further, that the hydrogen ion concentrations of the 

 medium converged toward the optimum as proteolysis proceeded. 

 From this point it will be carried into specific fields of application 

 in agriculture. 



Part II. — The method established in Part I. has been employed 

 to differentiate the proteolytic activity of Streptococcus erysipe- 

 latis and Streptococcus lacticus, organisms of peculiar and mooted 

 significance in milk. It should be understood, however, that this 

 is only a preliminary statement, and an exhaustive study is a 

 matter of the future. 



Requests for bulletins should be addressed to the 

 Agricultural Experiment Station, 



Amherst, Mass. 



