The invention relates to an isolated polynucleotide from Corynebacterium glutamicum having a polynucleotide sequence which codes for the carbon starvation protein A (cstA) gene, and a host-vector system having a coryneform host bacterium in which the cstA gene is present in enhanced form and a vector which carries at least the cstA gene according to SEQ ID NO: 1, and the use of polynucleotides which comprise the sequences according to the invention as hybridization probes.