In this study, enzymatic removal of bisphenol A (BPA) from the aqueous medium was investigated through the generation of water-insoluble oligomers, and this procedure was applied to removal of bisphenol derivatives. The experimental parameters, such as the temperature, pH value, enzyme concentration, and concentration and molecular weight of polyethylene glycol (PEG), were determined for the laccase-catalyzed treatment of BPA. The optimum conditions were determined to be pH 7.0 and 40°C in the absence of PEG. Water-insoluble oligomers generated under these conditions were readily removed by filtration or centrifugation. The optimum pH value was decreased to 5.0 in the presence of PEG and the laccase dose was reduced to one-fiftieth of that in the absence of PEG. This indicates that the addition of PEG protects the enzymatic activity and prevents capture of laccase molecules in the oligomers. The oligomers generated in the presence of PEG were removed from the aqueous medium by filtration with a membrane filter or by centrifugation. The oligomers were completely filtrated out with a filter paper by decreasing the pH value to 3.0. In addition, several bisphenol derivatives were also treated and subsequently removed by adjusting the laccase dose in the presence of PEG using the above procedure.
Keywords: Laccase; bisphenol A; bisphenol derivatives; polyethylene glycol; water-insoluble oligomer.