Preparation of enterochelin from Escherichia coli

A convenient method has been developed for the preparation of enterochelin, the natural iron carrier produced by Escherichia coli. The method employs a mutant strain which is unable to transport the ferric-enterochelin complex into the cell and which excretes large quantities of enterochelin into the culture medium. The addition of excess iron to the medium allows the enterochelin to accumulate as the ferric-enterochelin complex which is purified by ion-exchange chromatography and then dissociated and the free enterochelin further purified by differential extraction and crystallization. The enterochelin is isolated in good yield and appears to be of high purity as judged by a number of criteria.