Abstract: The present invention discloses an improved process for the preparation of 6-amino penicillanic acid (6-APA) from a fermentatively produced N-substituted penicillin comprising the steps of extraction of the N-substituted penicillin compound as present in a fermentation broth or fluid to an organic solvent, back extraction of the N-substituted penicillin compound to water, treatment of the aqueous phase with a penicillin acylase and isolation of the 6-APA from the thus-obtained conversion solution by crystallization. Further improvements comprise extraction of the side chain to an organic solvent and isolation of 6-APA from the thus-obtained aqueous phase using a specific crystallization process.