Disclosed herein is an isolated polynucleotide comprising a polynucleotide sequence chosen from the group consisting of a) polynucleotide which is identical to the extent of at least 70% to a polynucleotide which codes for a polypeptide which comprises the amino acid sequence of SEQ ID NO:2, b) polynucleotide which codes for a polypeptide which comprises an amino acid sequence which is identical to the extent of at least 70% to the amino acid sequence of SEQ ID NO:2 c) polynucleotide which is complementary to the polynucleotides of a) and b) and d) polynucleotide comprising at least 15 successive nucleotides of the polynucleotide sequence of a), b) or c), and processes for the fermentative preparation of L-amino acid with amplification of the zwa1 gene in the coryneform bacteria employed.