The invention relates to a genetically modified coryneform bacterium, the fadD15 gene of which is amplified, and an isolated polynucleotide which codes for acyl-CoA synthase from coryneform bacteria, and also a method for the fermentative preparation of L-amino acids with amplification of the fadD15 gene in the bacteria and the use of the polynucleotide as a primer or hybridization probe.