Phenolic compounds are present in different concentrations in the effluent from numerous industrial and agricultural activities. These compounds are harmful to living organisms due to their high toxicity, hence indicating a serious environmental concern. Although conventional methods such as chemical, physical, and physicochemical procedures have been widely used for treating phenol-contaminated wastewaters, they are not useful owing to some shortcomings. Compared to conventional procedures, much attention has been recently devoted to enzymatic methods because of high catalytic efficiency, mild operating conditions and environmentally friendly feature. Among various enzymes, laccases have demonstrated a superior potential for removing phenolic contaminants. Thus, this review summarizes the up-to-date literature on the use of free and immobilized laccases from different microbial source in the degradation and remediation of phenolic pollutants in batch processes and continuous reactors. In general, examples through the review approve that free laccases as well as immobilized laccases onto inorganic, organic (natural or synthetic) and hybrid supports show excellent performance in the remediation of phenolic compounds from wastewater. In contrast to immobilized laccases, free laccases suffer from high prices, low operative stability, and inability to recover and reuse in their native forms. Moreover, the possible mechanisms associated with oxidation of phenolic compounds by the laccase-catalyzed systems are assessed.
