Heterophase Synthesis of Humic Substances at Low Substrate Concentrations and Flow-Through Conditions

Abstract— Humic substances (HS) are heterogeneous and polydisperse compounds formed in soils, sediments waters during the decay transformation of organic residues (the process called humification). The role extracellular free-radical condensation reactions (secondary synthesis) formation HS is a subject debate. Here we have studied from mixture monomers under dynamic conditions at low substrate concentrations presence laccase fungus Coprinus comatus F-2940. Laccase was immobilized on kaolinite modified with aluminum hydroxide. We investigated some properties enzyme, reactivity phenolic acids amino laccase. optimum 2.6-dimethoxyphenol (2.6-DMP) oxidation by free pH 6.0. Upon immobilization, it shifted to acidic region (pH 4.4), thermal stability decreased, however kinetic parameters 2.6-DMP remained unchanged. In terms (% conversion laccase) individual series: caffeic (72) > ferulic (53) gallic = syringic (43) protocatechuic (5.5) vanillic p-hydroxybenzoic (0). acids, acid most efficiently oxidized (50%), while other were comparable amounts (13–17%). increased lysine. When gallic, protocatechuic, syringic, (0.01 mM each) lysine (0.02 mM) passed through flow-through microcolumn, effectively reaction products bound mineral phase, staining dark. According high performance liquid chromatography, molecular weights extracted phase did not exceed 900 Da, thus fulvic acid-like formed. Results study suggest an important heterophase composition organo-mineral complexes.