OPTIMIZATION OF PHENOL REMOVAL BY A FUNGAL PEROXIDASE FROM COPRINUS-MACRORHIZUS USING BATCH, CONTINUOUS, AND DISCONTINUOUS SEMIBATCH REACTORS

The use of a peroxidase from the fungus Coprinus macrorhizus for the r emoval of toxic organics from synthetic wastewater is explored in this study. Removal of phenols demonstrated a dependence of enzyme lifetim e on enzyme concentration in batch reactors. Maximum removal of phenol under optimal conditions in a batch reactor at enzyme activity above 0.3 U ml(-1) and up to 1.2 U ml(-1) was 53% in the present study. Cont inuous addition of C. macrorhizus peroxidase (CMP) to the reactor over periods varying from 0.5 to 3 h did not improve the removal. Similarl y, continuous addition of H2O2 did not improve the removal of phenol. A colorimetric assay for H2O2 indicated its depletion in the batch rea ctors. H2O2:phenol stoichiometry was greater than one if all the H2O2 was added at the beginning of the reaction. Instability of the H2O2 an d possible decomposition by contaminating catalase in the sample prepa ration are two possibilities for its depletion. To overcome this deple tion in the reactors regardless of the enzyme concentration, discontin uous addition of either CMP or H2O2 or both was adopted. Significant i mprovement in phenol removal (90%) was obtained when either H2O2 or CM P was added in three discrete aliquots over 0.5 h. With discontinuous addition of both reactants, the amount of CMP could be reduced to 0.3 U ml(-1) while achieving 91% removal of phenol at equimolar concentrat ion of H2O2. Thus, discontinuous addition of the reactant(s) increased the turnovers obtained by CMP and conserved the 1:1 phenol to peroxid e stoichiometry in the clearance reaction. Spectral observation of til e CMP utilized in this study showed the presence of a contaminating cy anide-like complex of the enzyme, as was observed by another group usi ng a similar microbial peroxidase.