Biotransformation of soil humic acids by blue laccase of Panus tigrinus 8/18: an in vitro study |
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Authors: | A.G Zavarzina A.A Leontievsky S.Ya Trofimov |
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Affiliation: | a Department of Soil Science, Moscow State University (MSU), Moscow 119899, Russian Federation b Institute of Biochemistry and Physiology of Microorganisms, Russian Academy of Sciences (IBPM RAS), Pushchino, Moscow Region 142292, Russian Federation |
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Abstract: | We describe here the role of the polyphenoloxidases in the oxidation of recalcitrant soil organic compounds and consider what changes occur in their structure during experiments on the biotransformation of soil and peat-derived humic acids (HA). These transformations were carried out by laccase (EC 1.10.3.2.) of the white-rot basidiomycete Panus tigrinus 8/18. It was shown that purified laccase alone is capable both of polymerizing and depolymerizing HA in vitro. The direction of transformations depends on the nature and properties of HA. Those fractions of HA are affected by laccase, which cause the lowest inhibitory effect on the enzyme. Contrary to previous studies depolymerization of HA was not necessarily accompanied by decolorization: chernozem-derived HA showed increase in absorbance of its aqueous solution in the region of 240-500 nm during depolymerization, while peat-derived HA showed decrease in absorbance throughout the entire spectrum during polymerization. All studied HA were competitive inhibitors of laccase towards oxidation of synthetic substrate 2,2′-azino-bis-(3-ethylthiazoline-6-sulfonate) (ABTS). When studying the nature of the inhibitory effect, it was shown that more ‘hydrophobic’ HA as well as more ‘hydrophobic’ HA fragments were stronger inhibitors of blue laccase. |
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Keywords: | White rot fungus Laccase Humic acids Biodegradation |
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