This monograph describes many applications of peroxidase-based biocatalysis in the biotechnology industry. The need for such a book emerges from the considerable amount of new data regarding the phylogeny, reaction mechanisms, thermodynamic characterization and structural features of fungal and plant heme peroxidases that has been generated in the past 10 years, since the last specialized book on peroxidases was published. The aim of this book is to present recent advances on such basic aspects as evolution, structure-function relation and catalytic mechanism as well as applied aspects, such as bioreactor and protein engineering, to provide the tools for rational design of enhanced biocatalysts and biocatalytic processes.