The present invention relates to a fermentation medium for cultivating Corynebacterium diphtheriae. The present invention also relates to the use of the fermentation medium in processes for obtaining diphtheria toxin from the Corynebacterium diphtheriae bacteria being cultivated and the preparation of vaccines using the diphtheria toxin obtained in the processes. The present invention further relates to a purification and detoxification processes specifically adapted for preparing a diphtheria toxoid for inclusion into a vaccine.