Screening metagenomic libraries for laccase activities

Laccases are multi-copper oxidoreductases (benzenediol:oxygen oxidoreductases, EC 1.10.3.2) able to oxidise a wide variety of phenolic and non-phenolic compounds. They are useful enzymes for a variety of applications, including bioremediation and craft pulp bio-bleaching as the most significant ones. There is a considerable interest to find new laccases through the exploration of biological diversity. Laccases have been found in plants, insects, and bacteria but predominantly in fungi: these enzymes have been documented in about 60 fungal strains. Microbial diversity constitutes a largely unexplored treasure chest with new laccases with a good potential for basic science and biotechnology. At present, due to our inability to cultivate most microbes, the only means of accessing the resources of the microbial world is to harvest genetic resources ("metagenomes"), which can further on be subjected to extensive screening programs. In this chapter, we provide an overview of screening methods to identify laccase-encoding genes from environmental resources.