Adeney — Aerobic Bacterial Fermentation. 



17 



We can distinguish, with close approximation, between the pro- 

 ducts due to enzymic action and those due to respiratory change thus: 

 assuming that the 0*022 grm. of nitrogen as ammonia was wholly 

 the result of hydrolysis of urea, its equivalent of carbon dioxide is 

 17*54 c.c. This leaves a balance of 33*11 c.c. of carbon dioxide as due 

 to respiratory change exerted upon the E-ochelle salt. Assuming the 

 oxidation to have taken place according to the equation — 

 2C4H4KI^"a06 + 5O2 = 8CO0 + 4H2O + 2KNaO, 



the volume of oxygen consumed is to the volume of carbon dioxide 

 formed as 5 : 8. That is, the balance of 33-11 c.c. of carbon dioxide 

 should be equivalent to 20*7 c.c. of oxygen. The analysis shows 

 a consumption of 23*1 c.c. of that gas. 



We are therefore warranted in assuming that the respiratory 

 changes were practically confined to the Eochelle salt, and the enzymic 

 action to the urea. It may then be gathered from the analytical 

 results that 74*17 per cent, of the carbon in the former substance was 

 converted into carbon dioxide, and that at the same time 20*96 per 

 cent, of the latter substance suffered hydrolysis. 



Direct quantitative evidence is also afforded by these results, 

 showing that the hydrolysis of urea during fermentation of the more 

 favourable nutrient substance, Rochelle salt, is entirely due to enzymic 

 action, and not to any other physiological process. 



A further feature of interest exhibited by the results recorded in 

 Table 7 is the evidence which the figures for the dissolved atmospheric 

 nitrogen afford of the " fixation " of that gas during the fermentation. 

 The different values obtained before and after fermentation are all, 

 with the exception of I^o. 13, decidedly too large to ascribe to 

 experimental errors. 



Conclusion, 



1. The organisms capable of initiating and effecting the hydrolysis 

 of urea appear to exert that change entirely by enzymic action. 



2. When the conditions of fermentation are such that ui'ea is 

 subject to the physiological process of respiration — in other words, 

 when urea is the sole nutrient organic substance present — it undergoes 

 only partial hydrolysis, the greater part of it undergoing a process of 

 oxidation ; thus : — 



3COK0H + 3O2 = 3CO3 + N2O3 + 4NH3, 



the result of the respiratory or energetic metabolic requirements of the 

 organisms. 



