Polyethylene glycol-enhanced removal of 2,4-dichlorophenol and 4-chlorophenol by peroxidase from shepherd’s purse (Capsella bursa-pastoris)

Plant-derived peroxidases, a class of oxidoreductases, can detoxify phenolic organic contaminants by catalyzing oxidative coupling reactions in the presence of hydrogen peroxide (H 2 O 2 ) as an electron acceptor. In this study, peroxidase was extracted from the roots of shepherd’s purse ( Capsella bursa-pastoris ) collected from three different regions in South Korea (Daejeon, Daegu, and Goesan), and the enzyme activities of the extracts were compared. Subsequently, the root extract from the region exhibiting the highest enzyme activity was used to remove chlorophenols, specifically 2,4-dichlorophenol (2,4-DCP) and 4-chlorophenol (4-CP), from contaminated water. Among the samples, the shepherd’s purse root extract (SPRE) from Daejeon showed the highest peroxidase activity (83.1 units g −1 ), followed by those from Daegu (22.3 units g −1 ) and Goesan (12.3 units g −1 ). Treatment with 0.20 units mL −1 of Daejeon SPRE in the presence of 1 mM H 2 O 2 removed 97% and 80% of 2,4-DCP and 4-CP, respectively, within 24 h from water initially containing 50 mg L −1 of each compound. To further enhance the peroxidase-mediated contaminant removal, polyethylene glycol (PEG), a known reaction stabilizer, was added at 100 mg L −1 . The PEG addition enabled > 99% removal of both chlorophenols, even when the dose of Daejeon SPRE was reduced fourfold (0.05 units mL −1 ). These results demonstrate that the combined treatment of SPRE and PEG provides an efficient biochemical strategy for the remediation of aquatic environments contaminated with chlorophenol compounds.