The use of biocatalysts, employed either as isolated enzymes or whole microbial cells, offers a remarkable arsenal of highly selective transformations for state-of-the-art synthetic organic chemistry. Over the last two decades, this methodology has become an indispensable tool for asymmetric synthesis, not only at the academic level, but also on an industrial scale. This well-established textbook on biocatalysis provides a basis for undergraduate and graduate courses in modern organic chemistry, as well as a condensed introduction into this field. After a basic introduction into the use of biocatalysts - principles of stereoselective transformations, kinetics and enzyme properties - the different types of reactions are explained according to the 'reaction principle', such as hydrolysis, reduction, oxidation, C-C bond formation, etc. Special techniques, such as the use of enzymes in organic solvents, immobilization techniques and the use of modified enzymes, are treated in a separate section. A final chapter deals with the basic rules for the safe and practical handling of biocatalysts. In this revised and corrected 5th edition, emphasis has been given to an improved didactic style in order to facilitate a deeper understanding of the underlying principles. New developments, such as dynamic resolution, stereo-inversion and enantio-convergent processes are included.