A mineral support and biotic catalyst are essential in the formation of highly polymeric soil humic substances

The hypothesis was proposed that highly polymeric humic substances in the mineral horizons of soils in a temperate humid climate originate from polymerization of water-soluble structural precursors directly on mineral surfaces under the catalytic effect of immobilized phenoloxidases (heterophasic bi...

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Bibliographic Details
Published in:Eurasian soil science 2006-12, Vol.39 (S1), p.S48-S53
Main Author: Zavarzina, A G
Format: Article
Language:English
Subjects:
Catalysis
Humic acid
Humid climates
Kaolinite
Methylene blue
Oxidases
Oxidation
Phenols
Polymerization
Soil horizons
Soils
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Summary:The hypothesis was proposed that highly polymeric humic substances in the mineral horizons of soils in a temperate humid climate originate from polymerization of water-soluble structural precursors directly on mineral surfaces under the catalytic effect of immobilized phenoloxidases (heterophasic biocatalysis). This hypothesis was confirmed by a laboratory experiment using a mixture of monomeric phenols and nitrogenous compounds as structural precursors, fungal laccase as a biotic catalyst, and a hydroxyaluminum-kaolinite complex as a mineral support. Enzymic oxidation of phenolic precursors on the mineral surface was substantially more rapid than abiotic oxidation and led to synthesis of a highly polymeric fraction with a molecular weight over 75 kDa. These products were not produced on the mineral with an absence of laccase (abiotic catalysis) or in solution without the mineral matrix (homogeneous catalysis).
ISSN:1064-2293
1556-195X
DOI:10.1134/S1064229306130096