Comparison of Laccases and Hemeproteins Systems in Bioremediation of Organic Pollutants

Aim: Laccases and peroxidases have attracted great interest for industrial and environmental applications. These enzymes have a broad substrate range and a robust oxidizing ability. Moreover, using mediators or co-oxidants makes it possible to increase their catalytic activity and extend their substrate scope to more resistant chemical structures. Background: Fungal laccases and ligninolytic peroxidases, mainly lignin and manganese peroxidases, are the privileged oxidoreductases for bioremediation processes. Nonetheless, an increasing diversity of laccases and peroxidase-type enzymes has been proposed for environmental technologies. Objective: This article aims to provide an overview of these enzymes and compare their applicability in the degradation of organic pollutants. Methods: Fundamental properties of the proteins are covered and applications towards polycyclic aromatic hydrocarbons (PAHs) and pesticides are specially focused. Results: Laccases are multicopper oxidases initially studied for applications in the pulp and paper in-dustry but able to oxidize a variety of environmentally concerning compounds. Relying on O₂, laccases do not require peroxides nor auxiliary agents, like Mn²⁺, although suitable redox mediators are needed to attack the more recalcitrant pollutants (e.g., PAHs). True and pseudo-peroxidases use a stronger oxi-dant (H₂O₂) and the redox chemistry at the heme site generates high potential species that allow the oxidation of dyes and some pesticides. Conclusion: Lately, research efforts have been directed to enzyme discovery, testing with micropollu-tants, and improving biocatalysts’ stability by immobilization and protein engineering. Further under-standing of the effects of natural media components and solvents on the enzymes might lead to compet-itive enzymatic treatments of highly toxic media.