Enzyme-Catalyzed Oxidation of 17β-Estradiol Using Immobilized Laccase fromTrametes versicolor

Many natural and synthetic estrogens are amenable to oxidation through the catalytic action of oxidative enzymes such as the fungal laccase Trametes versicolor . This study focused on characterizing the conversion of estradiol (E 2 ) using laccase that had been immobilized by covalent bonding onto silica beads contained in a bench-scale continuous-flow packed bed reactor. Conversion of E 2 accomplished in the reactor declined when the temperature of the system was changed from room temperature to just above freezing at pH 5 as a result of a reduced rate of reaction rather than inactivation of the enzyme. Similarly, conversion increased when the system was brought to warmer temperatures. E 2 conversion increased when the pH of the influent to the immobilized laccase reactor was changed from pH 7 to pH 5, but longer-term experiments showed that the enzyme is more stable at pH 7. Results also showed that the immobilized laccase maintained its activity when treating a constant supply of aqueous E 2 at a low mean residence time over a 12-hour period and when treating a constant supply of aqueous E 2 at a high mean residence time over a period of 9 days.