Abstract
The synthesis of L-isoleucine by Corynebacterium glutamicum involves 11 reaction steps, with at least 5 of them regulated in activity or expression. Using gene replacement we constructed a vector-free C. glutamicum strain having feedback-resistant aspartate kinase and feedback-resistant homoserine dehydrogenase activity. Isogenic strains carrying in addition one or several copies of feedback-resistant threonine dehydratase were made and their product accumulations compared. With strain SM1, with high threonine dehydratase activity, accumulation of 50 mM L-isoleucine was achieved, whereas with the parent strain only 4 mM L-isoleucine was obtained. Applying a closed-loop control fed-batch strategy to strain SM1 a final titre of 138 mM L-isoleucine was achieved with an integral molar yield of 0.11 mol/mol, and a maximal specific productivity of 0.28 mmol (g h)-1. This shows that high L-isoleucine yields can be obtained in the presence of one copy of feedback-resistant homoserine dehydrogenase by applying the appropriate fermentation strategy. In addition, the specific profiles of 2-oxoglutarate and pyruvate accumulation during fermentation revealed a major transition of the metabolism of C. glutamicum during the fermentation process.
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Received: 16 October 1995/Received revision: 21 December 1995/Accepted: 8 January 1996
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Morbach, S., Kelle, R., Winkels, S. et al. Engineering the homoserine dehydrogenase and threonine dehydratase control points to analyse flux towards L-isoleucine in Corynebacterium glutamicum . Appl Microbiol Biotechnol 45, 612–620 (1996). https://doi.org/10.1007/s002530050738
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DOI: https://doi.org/10.1007/s002530050738