CHARACTERIZATION OF REACTION-PRODUCTS FROM THE ENZYME-CATALYZED OXIDATION OF PHENOLIC POLLUTANTS

Phenol oxidizing enzymes such as peroxidases, laccases and polyphenol oxidases (tyrosinases) have been proposed for use in wastewater treatment. Few of the previous studies with these enzymes have focused on characteristics of reaction products relevant to waste treatment objectives, which must be known if enzyme technology is to be developed as a viable treatment process. In addition, little attention has been paid to the potential differences among different phenol oxidizing enzymes with respect to product characteristics and other factors of importance for full-scale applications. Work in this study focused on chromatographic and acute toxicity (by Microtox(R) assay) analysis of reaction products from the enzyme catalyzed oxidation of several regulated phenolic compounds, using the enzymes chloroperoxidase, horseradish peroxidase, lignin peroxidase, manganese peroxidase and mushroom polyphenol oxidase. The nature and distribution of reaction products from a given target phenol depended on the enzyme used and on reaction pH for otherwise constant reaction conditions. In some cases, differences in product characteristics (as judged through chromatography) corresponded to differences in toxicity as well. The compounds 4-chlorophenol, p-cresol and pentachlorophenol were detoxified by at least one of the enzymes tested, whereas enzymatic oxidation of 2-nitrophenol, 4-nitrophenol, 2-chlorophenol, 0-cresol and phenol either increased the toxicity or had a negligible effect.