ZYMOLOGY FERMENTS AND FERMENTATIONS 213 



substances undergoing precipitation, carry with them any ferments that 

 may be present. 



i. Under ordinary condition the enzymatic action of the ferment is not 

 complete. For example, the zymase cloes not catalyze all of the sugar in 

 a solution into alcohol and carbonic acid gas. The process can, however, 

 be made to proceed to completion by removing the end products as they 

 are formed (as may be done by means of a dialyzable bag suspended in a 

 stream of water). The reason why the process is not completed under 

 ordinary conditions is because the ferment has a synthetic power, re- 

 combining the accumulating end products into sugar. The catalytic 

 process is, however, always much more active than the synthetic process, 

 at least during the earlier stages of the fermentation. Gradually the 

 catalytic process decreases until a stage is reached where the catalytic and 

 synthetic processes are approximately equalized. 



j. The queston is often asked why are the cells which form the ferment 

 and the organs in which they are active, not digested or catalyzed by the 

 ferment? While the question is as yet not definitely settled, it is highly 

 probable that the auto-digestion of ferment-producing cells, tissues and 

 organs, is prevented by the formation of anti-ferments or anti-bodies, com- 

 parable to the anti-bodies or anti-toxins formed in cells, tissues, and or- 

 gans, to neutralize the toxins of disease. It is known, for example, that 

 under certain pathological conditions, localized digestion of stomach tissue 

 may take place, as in ulcer. In such cases the anti-ferment is probably 

 non-existent or in some way inactivated, neutralized or destroyed. 



k. In some instances it is known that the ferment or enzyme is formed 

 as the result of a pro-ferment or zymogen, activated by a second sub- 

 stance. For example, pepsin is not formed in the stomach cells, but 

 rather in the cavity of the stomach from the pepsinogen which is formed 

 in the mucous cells of the stomach, activated by the free hydrochloric acid 

 present. 



1. Considered from the standpoint of their relationship to the cells 

 which form them, enzymes may be divided into three groups as follows: 

 a. Those which normally act dissociated from the cells which form them, 

 as ptyalin, pepsin, rennet, diastase, etc. b. Those which normally act 

 in association with the cells that form them but which may be isolated and 

 will then continue the fermentation, as yeast ferments; and c. Those 

 fernebts which thus far have not been separated or isolated from the cells 

 which form them, as many of the bacterial enzymes. 



m. The smallest amount of enzyme will catalyze as much fermentable 

 material as a large amount, provided it is allowed to act for the necessary 

 length of time. On 'the other hand, it holds that the rate of fermentation 

 is directly proportioned to the amount of enzyme in action. 



