The ligninolytic enzymatic consortium, formed mainly by nonspecific oxidoreductases (laccases, peroxidases, and peroxide-supplying oxidases), is a potentially powerful multipurpose tool for industrial and environmental biotechnology. In nature, these enzymes are typically produced by basidiomycete white-rot fungi that are involved in lignin decay. Thanks to their broad substrate specificity, high redox potential, and minimal requirements, these enzymes have many potential applications in the field of green chemistry, including the production of biofuels, bioremediation, organic syntheses, pulp biobleaching, food and textile industries, and the design of bionanodevices. The implementation of this enzymatic armoury in different biotechnological sectors has been hampered by the lack of appropriate molecular instruments (including heterologous hosts for directed evolution) with which to improve their properties. Over the last 10 years, a wealth of directed evolution strategies in combination with hybrid approaches has emerged in order to adapt these oxidoreductases to the drastic conditions associated with many biotechnological settings (e.g., high temperatures, the presence of organic co-solvents, extreme pHs, the presence of inhibitors). This chapter summarizes all efforts and endeavors to convert these ligninolytic enzymes into useful biocatalysts by means of directed evolution: from functional expression to stabilization and beyond.

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