120 Decomposition of Plant and Animal Residues 



Table 23. 



Protein 



Edestin 



Gli 



Zeiii 



Casein 



Decomposition of Vegetable and Animal Proteins by Different 

 Microorganisms (from Waksman and Starkey) 



Period of decomposition, 9-15 days. 



This formula is not generally accepted. Certain investigators 

 proposed the formula of substituted phenyl-propane groups linked 

 together. The phenyl group has a hydroxyl in the para position 

 and a methoxyl in the meta. The propane may have a double bond, 

 thus becoming a propene, and a hydroxyl. It is also claimed that 

 nitrogen is present as a tertiary amine in a linkage similar to that 

 in pyridine. Bondi and Meyer claimed that lignins of various plants 

 are built out of three of these units, having a molecular weight of 

 about 650. They formed two methoxyls in grass lignins and one 

 methoxyl in leguminous lignins, each lignin containing two phenolic 

 hydroxyls and one aliphatic. 



Lignins are found in virtually all plants in varying concentrations, 

 depending upon the nature of the plant and the degree of its ma- 

 turity, usually to the extent of 5-30 per cent. The more mature the 

 plant, the higher its lignin content; young plants have comparatively 

 little lignin, whereas mature plants have a high lignin content. 



In the decomposition of plant materials under natural conditions, 

 lignin tends to accumulate, since it is more resistant to decomposi- 

 tion than are the carbohydrates and proteins (Table 24). Fir wood, 



