Conversion of lignocellulosic materials to useful, high value products normally requires a pre-treatment step to transform or deconstruct the recalcitrant and heterogeneous lignin fraction. The development of “green tools” for the transformation of lignocellulosic feedstocks is in high demand for a sustainable exploitation of such resources. This multi-faceted challenge is being addressed by an ever-increasing suite of ligninolytic enzymes isolated from various sources. Among these, fungal laccases are known to play an important role in lignin degradation/modification processes. The white-rot fungus Pleurotus ostreatus expresses multiple laccase genes encoding isoenzymes with different properties. The availability of established recombinant expression systems for P. ostreatus laccase isoenzymes has allowed to further enrich the panel of P. ostreatus laccases by the construction of mutated, “better performing” enzymes through molecular evolution techniques. New oxidative catalysts with improved activity and stability either at high temperature and at acidic and alkaline pH have been isolated and characterized.