Role of various inorganic components and enzymes in the formation of humic substances

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Role of various inorganic components and enzymes in the formation of humic substances was investigated.The promotina effect of Mn oxide on the formation of artificial humic substances was much higher than that of Fe, Al, and Si oxides. The accelerating effects of montmorillonite and tephroite were the highest among the respective mineral groups studied. Among all inorganic materials studied, the catalytic power of tephroite and especially Mn oxide was most striking.The oxidative coupling enzymes such as tyrosinase were able to catalyze the synthesis of artificial humic substances. However, the catalytic effect was remarkably influenced by the substrate specificity of enzyme. For example, the tyrosinase promoted the synthesis of humic substances from o-phenolic compounds to a larger extent compared with the other phenolics.The formation of humic substances was proceeded through radical reactions, and the humic substances with a high degree of humification mainly consisted of stacked fractions of two and three layers.The physicochemical and spectroscopic properties of artificial humic substances were similar to those of natural humic substances.From the results obtained, it is tentatively concluded that various inorganic components and enzymes play an important role in the formation of humic substances.