220 NUTRITION AND METABOLISM 



Probably all cells produce several enzymes Microorganisms 

 feeding upon various foods must form various enzymes. Frequently 

 several enzymes are necessary for the decomposition of one com- 

 pound. Rhizopus oryza uses three enzymes in order to form alcohol 

 from starch, first the diastase to change starch to maltose, then 

 maltase to change maltose to dextrose and finally alcoholase 

 to change dextrose to alcohol and carbon dioxide. The number of 

 enzymes formed by certain microorganisms is surprising. Asper- 

 gillus niger has the reputation of forming almost all enzymes which 

 have ever been found in microorganisms. Penicillium camemberti 

 produces (after Dox) erepsin, nuclease, amidase, lipase, emulsin, 

 amylase, inulase, raffinase, invertase, maltase and lactase. It has 

 been believed for a long time that certain enzymes are regular products 

 of the cell while others are formed only if the substance upon which 

 they act is present. According to Dox's investigations with Peni- 

 cillium camemberti, there is no evidence that enzymes not normally 

 formed by the organism in demonstrable quantities can be developed 

 by special methods of nutrition. The addition of a particular 

 food compound does not develop an entirely new enzyme, but stimu- 

 lates the production of the corresponding enzyme which is normally 

 formed, although in small amounts, under all conditions. 



