The feasibility of the catalysis of horseradish peroxidase (HRP) in supercritical CO²
was studied for the polymerization of p-cresol in the presence of H₂O₂. The reactions were performed at 40℃ and 74.8 atm (1100 psia) above the critical conditions of CO₂. In the initial tests with 2 mM of p-cresol and 1 mM of H₂O₂, more oligomers of p-cresol were produced as more HRP was added. This indicates that HRP is active in supercritical CO₂. HRP was not completely inhibited by H₂O₂ at concentrations up to20 mM. Increasing the initial concen- trations of p-cresol and H₂O₂ to 20 mM, respectively, resulted in the formation of precipitates which were undissolved either in water or in dimethylforamide (DMF). The effects of adding water and/or methanol as cosolvents on the reactivity of HRP were studied subsequently. When more than 13.3 mL of water per liter of reaction volume was added, the formation of precipitates was not observed. The reactivity of HRP was sustained when up to 11.8 mL of methanol per liter of reaction volume was added. In most cases conversion of p-cresol was less than 50% for 5 hours of reaction time.