The present invention relates to the provision of genetically modified microbial cells, such as yeast cells with an improved ability for producing L-ornithine and its derivatives. Overproduction of L-ornithine is obtained in the first place by the down-regulation or attenuation of specially selected genes, wherein said genes encode enzymes involved in the L-ornithine consumption and/or degradation pathways. Further L-ornithine production ability is improved by down-regulation, attenuation, deletion or overexpression of specially selected genes, wherein said genes encode enzymes and/or proteins involved in the L-ornithine ‘acetylated derivatives cycle’, L-glutamate synthesis pathways, subcellular trafficking, TCA cycle, pyruvate carboxylation pathway, respiratory electron-transport chain, and the carbon substrates' assimilation machinery. The invention additionally provides a method to produce L-ornithine with said modified eukaryotic cells.