Fungal Laccases and Their Potential in Bioremediation Applications

Basidiomycete white rot and litter-decomposing fungi secrete unspecific oxidative enzymes for degradation of aromatic polymer lignin. Recalcitrant organopollutants with structural similarities to lignin can also be degraded by these enzymes, i.e., laccases and class II heme peroxidases. Laccases belong to a superfamily of multicopper oxidases, which have been characterized in basidiomycete and ascomycete fungal species. Laccases catalyze one-electron transfer reactions from phenolic and low-redox-potential compounds with the concomitant reduction of molecular oxygen to water. In the presence of small molecular weight mediator compounds, the substrate spectrum of laccases expands to non-phenolic molecules and larger organic polymers. Fungal laccases have broad substrate range, and therefore they have attracted attention as “green catalysts” in different areas of biotechnology including bioremediation. Applications for fungal laccases are found in wastewater treatment, detoxification, and decolorization of industrial effluents as well as in bioremediation of contaminated soils. In this chapter, we describe the properties of fungal laccases, their reactions with mediator compounds, and their recombinant production in different host organisms. We also discuss the potential and challenges as well as the recent trends of the use of fungal laccases in bioremediation of wastewaters and soils contaminated with various xenobiotics.