COMPARATIVE STUDIES ON RESPIRATION. 



XII. A Comparison of the Production of Carbon Dioxide by 



Penicillium and by a Solution of Dextrose and 



Hydrogen Peroxide. 



By F. G. GUSTAFSON. 

 (Front the Laboratory of Plant Physiology, Harvard University, Cambridge) 



(Received for publication, June 11, 1920.) 



The writer has shown^ that the production of CO2 by Penicillium 

 chrysogenum is increased by acid and decreased by alkalies. The 

 next step is to investigate the mechanism by which CO2 is produced. 

 For this purpose it seems desirable to try to construct an artificial 

 system which would imitate the action of the fungus. 



In the experiments with Penicillium the oxidizable substance was 

 for the greater part dextrose, as the fungus was kept in a 0.5 per cent 

 solution of that substance. A 0.5 per cent dextrose solution was 

 therefore chosen as the basis of the artificial system. From a number 

 of available oxidizing agents hydrogen peroxide was chosen as being 

 the most promising. Dakin^ states that of the various oxidizing 

 agents hydrogen peroxide comes nearest to bringing about the same 

 reactions in vitro as normally take place within the organism. An 

 artificial system was accordingly made which consisted of a 0.5 per 

 cent solution of dextrose plus hydrogen peroxide.^ 



The experiments were performed in essentially the same manner 

 as those already described^ except that the artificial system was sub- 

 stituted for the fungus. In each experiment the hydrogen ion con- 

 centration was kept constant during the whole experiment and the 

 rate of production of CO2 was measured before and after the addition 



iGustafson, F. G., /. Gen. Physiol, 1919-20, ii, 617. 



^Dakin, H. D., Oxidations and reductions in the animal body, London, 1912. 



^ In these experiments "Dioxygen" was used, as it is nearly neutral and it 

 is stated by the makers to contain only 0.04 per cent of substances other than 

 water and hydrogen peroxide, no preservative being added. 



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