Soybean Peroxidase: An Alternative to Horseradish Peroxidase for the Treatment of Aqueous Solutions Contaminated with Chlorinated Phenols

In the presence of hydrogen peroxide, soybean peroxidase (SBP), an enzyme extracted from the soybean seed coat, catalyzes the polymerization of various chlorinated phenols in aqueous solution. The resulting polymer precipitates from solution and can be removed through a simple sedimentation or filtration process. Researchers have studied similar enzymes from other plant sources including horseradish peroxidase (HRP). Experiments for the study in question were performed to determine optimal environmental conditions such as pH, temperature, reaction time, substrate and additive concentrations as well as the reactor configuration. Generally, results obtained using SBP were similar to results published for HRP. However, under several conditions, SBP showed more potential for the treatment of chlorinated phenols. For example, the soybean enzyme functioned in a lower pH condition than what is reported for the horseradish enzyme. Also, SBP was significantly more efficient in removing 2,4-dichlorophenol from solution when the additive polyethylene glycol with a molecular weight of 8000 (PEG 8000) was present in solution than when the lower molecular weight PEG 3350 was present. Currently, the use of such a treatment process is limited by the cost of the enzyme, along with other factors. Experiments determined that the reactor configuration, mode of enzyme addition and the use of higher molecular weight PEG additives could significantly increase the removal efficiency of the process. In conclusion, SBP demonstrated itself to be as viable as HRP (if not more) in terms of removal effectiveness. In turn, a waste product from one process (soybean seed coat) may someday be used as an essential tool in the remediation of other waste compounds.