132 



PHYSIOLOGY OF BACTERIA 



As long as the enzyme content of the cell remains 

 constant, the increased temperature will cause an 

 increased rate of fermentation corresponding to the 

 normal temperature coefficient of the enzyme action. 

 The highest temperature at which the production of 

 enzyme is still equal to its deterioration, is the optimum 

 for fermentation. Beyond this point, the enzyme con- 

 tent of the cell must gradually decrease and the result is 

 the Tammann principle, i.e. the shifting with time of 

 the optimum from high to lower temperatures. In 

 fermentation by living organisms, the optimum does 

 not shift to the lowest temperature, but to the optimum 

 temperature at which the rate of fermentation remains 

 constant. 



The Tammann principle at temperatures above the 

 optimum can be seen in Table 25, which presents some 

 unpublished results by the author, and shows the CO2 

 pressure produced by bakers' yeast in pure sugar solu- 

 tion. The result is not very clear because the rate of 

 fermentation increased during the first hour. But the 

 gradual shifting of the optimum temperature from 44 "^ 

 to 32.5°C. is quite conspicuous. 



Table 25. — Rates op Fermentation at Super-optimal 



Temperatures 



(mm. of mercury pressure produced by yeast in sucrose solution in 5 



minutes) 



