Process for the preparation of L-3, 4-dihydroxyphenylalanine by aerobic fermentation of a microorganism

Process for the preparation of a L-3,4-dihydroxyphenylalanine, wherein L-3,4-dihydroxyphenylalanine is produced in a fermentation medium by aerobic fermentation of a recombinant microorganism having L-tyrosine-3-hydroxy-mono-oxtgenase activity and having at least the abilities to convert glucose or another carbon source into phosphoenol pyruvate (PEP) and into erothrose 4-phosphate (E4P), and to convert the PEP and E4P into L-phenylalanine, L-tyrosine and L-tryptophan, wherein the process comprises

• (i) a growth phase and a production phase, wherein L-3,4-dihydroxy-phenylalanine is produced in the fermentation medium and
• (ii) a downstream processing phase,
• characterized in that the L-3,4-dihydroxy-phenylalanine is produced from a carbon source and in that at least part of the production phase and/or downstream processing phase the pH is the range of from 1 to 7.