CHAPTER 13 

 METABOLIC PRODUCTS 



The most important product of fungus metabolism is carbon dioxide, 

 and the most important function of the fungi in the economy of nature 

 is the destruction of plant and animal remains. The use of fungi for 

 food antedates written history. The use of fvmgi for the preparation 

 of bread and wine developed as a household art. From the time of 

 Pasteur, the study of fermentation has led to an ever-increasing knowl- 

 edge and understanding of the activities of microorganisms. The pro- 

 duction of antibiotics and vitamins, alcohol and organic acids, and the 

 potential utilization of waste agricultural products are current fields of 

 research and industrial activity. For extensive treatment of these 

 subjects the reader is referred to Prescott and Dunn (1949) and Foster 

 (1949). 



DECOMPOSITION OF ORGANIC MATERIALS 



Brefeld (1908) called fungi "Organismen der Verwesung" and con- 

 sidered them to be indispensable agents in maintaining the essential- 

 element balance of nature. Saprophytic fungi and bacteria prevent the 

 accumulation of plant and animal debris and return the elements that 

 compose these materials to the storehouse of nature, where they are 

 reused by new generations of plants and animals. In this role, sapro- 

 phytic fungi are designated as "vegetable vultures" by Rolfe and Rolfe 

 (1926), for they act as scavengers in the plant world. 



Green plants assimilate carbon in the form of carbon dioxide. Waks- 

 man (1938) has assembled the data with regard to the amount of carbon 

 in the biosphere. It is estimated that the atmosphere contains 600 

 billion tons of carbon in the form of carbon dioxide, and plants are esti- 

 mated to remove 16 billion tons yearly. Thus, the carbon content of the 

 atmosphere is sufficient for about 40 years, if no carbon dioxide were 

 returned to the air. 



The complete destruction of plant and animal remains by fungi and 

 bacteria requires a long time, although some plant constituents, such as 

 soluble sugars and other carbohydrates, are quickly utilized. Presum- 

 ably the fungi are the most important organisms in this process. Other 

 plant constituents, such as the waxes and lignin, are attacked more 

 slowly. The more resistant constituents are slowly modified to form 



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