ENZYME-CATALYZED POLYMERIZATION AND PRECIPITATION OF AROMATIC-COMPOUNDS FROM AQUEOUS-SOLUTION

Horseradish peroxidase enzyme (HRP), once activated by hydrogen peroxi de, initiates the oxidation of a wide variety of aromatic compounds. R eaction products undergo a non-enzymatic polymerization to form water insoluble aggregates which are readily separated from solution. HRP wa s selected for application in wastewater treatment systems due to its stability and retention of its catalytic ability over wide ranges of p H and temperature. HRP activity was optimal between pH 5.7 and 8.5 wit h peak activity occurring at neutral pH. Activity increased with tempe rature up to 50-degrees-C and declined at higher temperatures due to t hermal inactivation. HRP was inactivated rapidly by hydrogen peroxide in the absence of an aromatic substrate. The efficiency of removal tha t was achieved was dependent on the nature of the aromatic undergoing treatment and the amount of enzyme provided due to the finite lifetime of the catalyst. Optimization of pH significantly improved catalytic efficiency with a corresponding savings in treatment costs. Optimal ca talytic lifetime of HRP was achieved in the pH range of 7 to 9 for the eight phenolic compounds treated. The minimum residual level to which aromatic substrates were removed from solution was independent of the starting concentration of the aromatic substrate. Enhanced removal of hard-to-remove compounds was noted when mixtures of aromatic substrat es were treated.