A comparative study of aromatic pollutants degradation using two different Peroxidases
Enzyme based degradation of organic pollutants is a promising new remediation approach due to the promiscuous nature of the technique, the wide range of available enzymes, and the scalability of the process. Oxidoreductases, specifically, peroxidases are the most popular class of enzymes that have been used for the degradation of organic pollutants. It is generously assumed that all peroxidases behave similarly and produce similar degradation products. Our main objective was to test the hypothesis that related peroxidases may act differentially towards the degradation of aromatic pollutants. Therefore, in this study, we have carried out detailed degradation studies on three model of aromatic pollutants using two of the most commonly used peroxidases – Soybean peroxidase (SBP) and Chloroperoxidase (CPO). Our studies show that these two enzymes have very different optimum conditions when degrading these aromatic pollutants. For example, SBP had a pH optimum of 4, whereas CPO is most active at pH 2-3. Additionally, SBP and CPO had very different thermal stabilities, with SBP showing full activity up until 80oC, which was very different than CPO, which was almost completely inactive at 60oC. HPLC analyses confirmed that both SBP and CPO transformed the all the aromatic pollutants into different compounds, which was further confirmed by LC-MS-MS studies. Furthermore, toxicological evaluation showed that SBP-based treatment was able to reduce the toxicity, while CPO treatment failed to eliminate the toxicity of the compounds. Our results show that related peroxidases may behave very differently when used for remediation purposes and points to the need for toxicity analysis of peroxidase degraded pollutants, as well as to carry out detailed mechanistic studies to identify the intermediates produced.