Heterophase Synthesis of Humic Acids in Soils by Immobilized Phenol Oxidases

Water‐soluble phenolic metabolites in lichens and their potential role in soil organic matter formation at the pre‐vascular stage

“…Phenolic coupling with N‐compounds and sugars is an important step in humification (Stevenson, ), which is one of the routes of aromatic C sequestration in SOM. Thus, lichen thalli contain soluble pre‐humic material, which can be leached out into the soil and may undergo further oxidative transformations to HS in biotic and abiotic heterogeneous condensation reactions (Huang & Hardie, ; Piccolo et al, ; Zavarzina, ).…”

“…Soluble phenolic compounds (PCs) comprise a characteristic and highly reactive part of soil organic matter (SOM). Their transformations in soil include complexation with metal ions (Andjelkovic et al, ), adsorption on to clays and oxyhydroxides (Moreau, Colette‐Maatouk, Gareil, & Reiller, ; Zavarzina, Ermolin, Demin, & Fedotov, ) and polymerization in the presence of oxidative catalysts (Huang & Hardie, ; Zavarzina, ). As a result, PCs have a profound effect on soil mineral and organic matrices, participating in element mobilization and mineral weathering and in formation of organic–mineral compounds.…”

“…Although this traditional view of SOM is currently criticized (Lehmann & Kleber, ) and new paradigms of SOM have been introduced (Lehmann & Kleber, ; Piccolo, Spaccini, Drosos, Vinci, & Cozzolino, ), existing experimental evidence suggests that the HS concept continues to be relevant to modern theories of SOM formation. In particular, polyphenol‐Maillard reactions catalyzed by soil minerals (Huang & Hardie, ), heterophasic polymerization reactions in the presence of clay‐bound laccase (Zavarzina, ) or oxidative and photo‐oxidative oligomerization reactions in the presence of immobilized biomimetic catalysts (Piccolo et al, ) show the importance of heterogeneous oxidative coupling reactions among phenolic monomers for aromatic carbon (C) sequestration in soils. Self‐condensation and co‐polymerization of soluble PCs to soil components might be a quantitatively significant route for HS formation at the pre‐vascular stage in the absence of phenolic polymers (such as lignin) in the starting material (Zavarzina & Zavarzin, ).…”

“…• Phenolic composition of SOM and humification processes at pre-vascular stage are largely overlooked • Soluble phenolic acids, aldehydes and ketones are quantified in lichens for the first time • Lichens are depleted in phenylpropanoids and enriched in syringyl structures and monophenols • Lichen-derived phenolic compounds are potential precursors of humic substances under cryptogam cover 1 | INTRODUCTION Soluble phenolic compounds (PCs) comprise a characteristic and highly reactive part of soil organic matter (SOM). Their transformations in soil include complexation with metal ions (Andjelkovic et al, 2006), adsorption on to clays and oxyhydroxides (Moreau, Colette-Maatouk, Gareil, & Reiller, 2013;Zavarzina, Ermolin, Demin, & Fedotov, 2018) and polymerization in the presence of oxidative catalysts (Huang & Hardie, 2009;Zavarzina, 2011). As a result, PCs have a profound effect on soil mineral and organic matrices, participating in element mobilization and mineral weathering and in formation of organic-mineral compounds.…”

“…More recently, a group of phenolic acids, aldehydes and ketones of p-hydroxyl, vanillyl and syringyl type (so-called lignin monophenols) were detected in lichens after oxidation of their tissue with CuO (Zavarzina et al, 2015). Compounds with methoxy-groups and o-diphenols, detected in lichens, are known for their strong reactivities in adsorption reactions (Zavarzina et al, 2018) and oxidative coupling in the presence of both biotic (Canfora, Iamarino, Rao, & Gianfreda, 2008;Zavarzina, 2011) and abiotic catalysts (Huang & Hardie, 2009). The content of water-soluble PCs in specific lichens (Zagoskina et al, 2013) correlates with the activities of phenoloxidases laccase and tyrosinase in their thalli (Zavarzina and Zavarzin, 2006).…”