The use of biocatalysts, employed either as isolated enzymes or whole cells, offers a remarkable arsenal of highly selective transformations for modern preparative organic chemistry. During the last decade, this methodology has now generally been accepted as a complementary method to the already existing tools. This first textbook on biocatalysis provides a basis for undergraduate and graduate courses in biocatalysis, as well as a condensed introduction into this field. After a basic introduction into the use of biocatalysts - principles of stereoselective transformations, kinetics, enzyme nomenclature and handling - the different types of reactions are explained according to the "reaction principle". The 4th edition includes new chapters on peroxidase reactions and on handling of biocatalysts.