Peroxidase-catalyzed coupling of phenol in the presence of model inorganic and organic solid phases.

Peroxidase-catalyzed oxidative coupling reactions of phenol in aqueous systems variously containing silica sand, cellulose, lignin, and polymethylstyrene were investigated. These four solid phase materials represent a broad spectrum of different natural geosorbent types in terms of their physicochemical characteristics. Each solid was found to influence peroxidase-catalyzed phenol coupling, either by mitigation of enzyme inactivation, by participation in cross-coupling, or by a combination of these two activities. Mitigation of enzyme inactivation was observed for those three of the four model solids found to adsorb the enzyme effectively; i.e., cellulose, silica sand, and lignin. Two solids, polymethylstyrene and lignin, were found to participate significantly in cross-coupling reactions. It is postulated that relatively hydrophilic solids can mitigate peroxidase inactivation by forming enzyme-solid associations. Aromatic structures or unsaturated C-C bonds were found to be features of the solid-phase materials that allowed them to participate in cross-coupling. The results have important implications for process feasibility assessment and the engineering design of soil/sediment remediation systems employing enzymatic coupling schemes.