Removal of aqueous phenol by Arthromyces ramosus peroxidase

Abstract

The removal of aqueous phenol by Arthromyces ramosus peroxidase (ARP), in the presence of high molecular weight polyethylene glycol (PEG) as a protective additive, was investigated to study (i) the stoichiometry between phenol removal and peroxide consumption, (ii) enzyme inactivation in the presence of excess hydrogen peroxide, and (iii) the effect of reactor operating mode on phenol removal. The stoichiometry was observed to increase with increasing phenol conversion, and reached a maximum value of 0.9 mol phenol/mol peroxide when nearly complete phenol conversion was achieved. Spectral scans indicated that P-670 did not form with ARP in the presence of high concentrations of peroxide and in the absence of a reducing substrate. As long as phenol concentration was not limiting, the turnover capacity varied by approximately 3% of its average value of 76 400. This indicates that only marginal improvement in the efficiency of enzyme use would be achieved by stepped addition of enzyme. Similarly, sequential addition of hydrogen peroxide over an extended period of time yielded only a slight improvement in phenol removal from the reaction mixture. Key words: Arthromyces ramosus peroxidase, enzyme inactivation, phenol removal, reactor operation, stoichiometry.