150 PHYSIOLOGY OF BACTERIA 



was a rapid liquifier, and the peptone seemed to exert a 

 retarding influence. Strept. bovis showed the greatest 

 gain in growth, as well as in titratable and potential 

 acidity. 



This experiment was repeated with Lact. acidophilus, 

 but no difference in the final acidities could be observed 

 whether 0.026 gm. or 5.000 gm. of bacteria were added 

 to the milk. It is not permissible, therefore, to general- 

 ize from the above results. 



The former results are not without analogy in the 

 realm of enzyme action. It has already been mentioned 

 that a concentrated solution of zymase (yeast juice) 

 will yield a higher final alcohol concentration than a 

 diluted one. The same is true with urease; a larger 

 amount of urea will be changed to ammonium carbonate 

 by a larger amount of urease. 



This increased amount of fermentation products by an increased 

 number of cells can not be accounted for by the assumption of an 

 equilibrium. If we assume, however, that the hmiting concentration 

 of fermentation products prevents only the regeneration of the 

 zymases by the cell, but not altogether their action, then a slow 

 fermentation will continue for some time after this point has been 

 reached. With large amounts of enzyme, it will take considerable 

 time before all of it has deteriorated, and during this time, a slow 

 fermentation will take place. A small amount of enzyme at the start, 

 however, will soon be completely inactivated, and fermentation comes 

 to an early stop at a comparatively low concentration of products. 



This explanation is just an attempt to account for the facts, with- 

 out any safe biological backing. Still, it would also account for the 

 very slow fermentation which continues for a while when the limiting 

 amount of fermentation products, or even a little more, has been 

 added to a concentrated suspension of active cells (p. 112). 



SUMMARY 



In some fermentations, the final amount of fermen- 

 tation products increases with the number of cells 



