L-Cystein-Bildung mit Corynebacterium glutamicum und optische Sensoren zur zellulären Metabolitanalyse

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L-Cysteine is a crucial amino acid and, alongside L-methionine, is the most abundant sulfur-containing molecule in cells, providing reduced sulfur for various sulfur compounds. Its significance extends to microbial growth and industries such as food, pharmaceuticals, and cosmetics, necessitating fermentation-based production. This study aimed to develop a L-cysteine producer using an efficient Corynebacterium glutamicum L-serine producing strain and to create metabolite sensors for detecting sulfur availability. Key findings include: (1) The L-serine producer Ser4, containing the plasmid pserACB, was modified to produce L-serine without a plasmid by integrating the feedback-resistant serAfbr gene, resulting in slight L-serine production. Strong expression of serAfbr, along with serC and serB, was essential for high L-serine yields. (2) Increased expression of the native cysE gene improved L-cysteine production from 0.95 ± 0.35 mM to 5.6 ± 0.8 mM, and with cysK expression, levels reached 7.3 ± 0.7 mM. Deleting genes for cysteine desulfurase AecD and homoserine acetyltransferase MetX, along with expressing the fpr2-cysIXHDNYZ operon, had a moderate impact on L-cysteine formation. (3) Metabolite sensors for O-acetyl-L-serine (OAS) and O-acetyl-L-homoserine (OAH) were developed, demonstrating increased fluorescence in response to elevated intracellular levels of these molecules. (4) The impact of the CysR regulator on L-cysteine