Improving lysine production by Corynebacterium glutamicum through DNA microarray-based identification of novel target genes

For the biotechnological production of L-lysine, mainly strains of Corynebacterium glutamicum are used, which have been obtained by classical mutagenesis and screening or selection or by metabolic engineering. Gene targets for the amplification and deregulation of the lysine biosynthesis pathway, for the improvement of carbon precursor supply and of nicotinamide adenine dinucleotide phosphate (reduced form) (NADPH) regeneration, are known. To identify novel target genes to improve lysine production, the transcriptomes of the classically obtained lysine producing strain MH20-22B and several other C. glutamicum strains were compared. As lysine production by the classically obtained strain, which possesses feedback-resistant aspartokinase and is leucine auxotrophic, exceeds that of a genetically defined leucine auxotrophic wild-type derivative possessing feed-back-resistant aspartokinase, additional traits beneficial for lysine production are present. NCg10855, putatively encoding a methyltransferase, and theamt A-ocd-soxA operon, encoding an ammonium uptake system, a putative ornithine cyclodeaminase and an uncharacterized enzyme, were among the genes showing increased expression in the classically obtained strain irrespective of the presence of feedback-resistant aspartokinase. Lysine production could be improved by about 40% through overexpression of NCg10855 or the amtA-ocd-soxA operon. Thus, novel target genes for the improvement of lysine production could be identified in a discovery-driven approach based on global gene expression analysis.