Biocatalytic treatment of cresols in aqueous solution with soybean peroxidase

Soybean peroxidase (SBP) from the seed coat is instrumental in catalyzing the oxidation of various aqueous aryl-amino and -hydroxyl compounds in the presence of hydrogen peroxide. This capability positions SBP as a promising agent for both industrial and domestic wastewater applications. To assess SBP's effectiveness in removing o-, m-, and p-cresol from water, experiments were conducted using a stirred batch reactor. The goal was to determine the optimal conditions for achieving at least 95% removal of these compounds. Key parameters examined included pH, SBP activity, and hydrogen peroxide concentration for 1.0 mM cresol. The experiments confirmed SBP's efficiency in eliminating the cresols from water. High-performance liquid chromatography identified the optimal conditions for removal of the isomers: for o-cresol, removal was achieved with an SBP activity of 0.7 U mL^-1, pH 9.0, and hydrogen peroxide concentration of 1.2 mM; for m-cresol, SBP 0.8 U mL^-1, pH 8.0, and hydrogen peroxide 1.1 mM; for p-cresol SBP 0.3 U mL^-1, pH 7.0, and hydrogen peroxide 1.0 mM. Half-lives under these conditions were 2-9 min. Mass spectrometry confirmed the formation of product oligomers up to the decamer stage, and residual UV analysis was consistent with the oligomerization-precipitation pathway. These findings highlight SBP's potential to significantly reduce o-, m-, and p-cresol levels in water, demonstrating its utility in environmental remediation efforts.