Polymeric lignin preparations, degradation

Synthetic humic acids have been prepared by a number of investigators over the past 50 years. Most of these preparations are based on a preference for a specific hypothesis for the origin of humic substances (1) partial degradation of lignin (2) chemical polymerization of microbial phenols or lignin monomers and amino acids (3) cell autolysis products (4) microbial synthesis (see Stevenson, 1982, Chapter 8 for review). 

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