Efficient degradation of various recalcitrant azo dyes in aqueous medium by immobilized Origanum vulgare peroxidase

Hybrid xerogels, constructed from organic and inorganic silanes, have emerged as materials with versatile applications. They have shown promising potential for immobilization as their chemical structures encompass the mechanical, thermal, and structural stability of inorganic compounds in synergy with the functionality and flexibility of organic compounds. Incorporating a magnetic core and preparation at the nanoscale multiply their attraction for enzyme immobilization. To evaluate how efficiently this technology works for the immobilization of a plant peroxidase, a novel peroxidase (POX_ov) from a famous medicinal herb, Origanum vulgare, was immobilized on magnetic nanoparticles of a hybrid xerogel obtained from tetraethyl orthosilicate and (3-aminopropyl)triethoxysilane. Immobilization boosted the physicochemical properties of the enzyme so that the immobilized POX_ov (I.POX_ov) could tolerate lower pHs and higher temperatures. It oxidized all types of the examined phenolic, catecholic, guaiacolic, and aniline diazo dyes, while the free POX_ov (F.POX_ov) failed to oxidize the last group. These improvements also made I.POX_ov capable of oxidizing the recalcitrant azo dyes carrying electron-withdrawing groups much faster than F.POX_ov. I.POX_ov was employed in 7 successive cycles of oxidation of both phenolic and guaiacolic dyes with an average efficiency of 69%. The efficacy of the immobilization method and I.POXov competency for the enzymatic remediation of polluted water resources have been quantitatively demonstrated.