Preliminary Evaluation of Reaction Products from Enzymatic Oxidation of Phenolic Pollutants

The enzymes horseradish peroxidase (HRP), chloroperoxidase (CPO) and polyphenol oxidase (PPO) were studied for their ability to oxidize the compounds o-cresol, p-cresol, 2-chlorophenol, 4-chlorophenol, 4-nitrophenol and pentachlorophenol. Except for 4-nitrophenol, all the compounds could be completely or partially degraded under the experimental conditions. Enzyme stability was studied, including thermal, peroxide dependent and mechanism-based (suicide) inactivation in the presence of phenolic substrates. HRP did not exhibit significant mechanism-based inactivation, in contrast to CPO and PPO. Different substrates also had different influence on HRP, CPO and PPO stability. Reaction products from phenolic pollutant oxidation were evaluated and compared using C[18]reverse phase HPLC, size-exclusion chromatography, uv-vis scanning and visual characterization. In general, both HRP and CPO tended to produce a mixture of non-polar and polar products relative to target compounds, CPO tended to produce more products, especially non-polar products, than HRP from a given target compound. PPO only formed polar products. Differences in substrate characteristics (including substituent position), pH and enzyme all had an influence on the number and type of reaction products observed. Experiments using combinations of enzymes indicated that CPO and PPO could oxidize products formed from HRP.Master of Science in Environmental Engineerin