The invention relates to a process for biochemical synthesis of 1,4-butanediamine in a microorganism having an increased level of an ornithine decarboxylase activity (increased ODC activity) as compared to the native level of the ornithine decarboxylase activity, wherein in the microorganism also an increased activity of N-acetylglutamate formation is present as compared to the native level of activity of N-acetylglutamate formation in the microorganism and wherein 1,4-butanediamine produced in the microorganism is excreted into a fermentation broth, and is recovered from the fermentation broth. The invention also relates to vectors, plasmids and hosts carrying a corresponding increased ODC activity and an increased activity of N-acetylglutamate formation.