L-tryptophan is produced at the AMINO GmbH (Frellstedt, FRG) via biocatalytical condensation of the amino acid L-serine with indole. As a biocatalyst, tryptophan synthetase is used which is produced in high activities by a natural mutant Escherichia coli strain. The enzyme mechanism and specificity and the individual process-parameters for the biotrans-formation procedure are explained as well as the purification process of educts and products. This includes a detailed description of the quality control of educts, intermediates and final product. The active ingredient L-tryptophan is subsequently used by AMINO’s subsidiary company esparma GmbH to produce and distribute the pharmaceutical Lyphan®. The quality management system and the production procedure for Lyphan are described and discussed.