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- Title
Improvement of l-Leucine Production in Corynebacterium glutamicum by Altering the Redox Flux.
- Authors
Wang, Ying-Yu; Zhang, Feng; Xu, Jian-Zhong; Zhang, Wei-Guo; Chen, Xiu-Lai; Liu, Li-Ming
- Abstract
The production of l-leucine was improved by the disruption of ltbR encoding transcriptional regulator and overexpression of the key genes (leuAilvBNCE) of the l-leucine biosynthesis pathway in Corynebacterium glutamicum XQ-9. In order to improve l-leucine production, we rationally engineered C. glutamicum to enhance l-leucine production, by improving the redox flux. On the basis of this, we manipulated the redox state of the cells by mutating the coenzyme-binding domains of acetohydroxyacid isomeroreductase encoded by ilvC, inserting NAD-specific leucine dehydrogenase, encoded by leuDH from Lysinibacillus sphaericus, and glutamate dehydrogenase encoded by rocG from Bacillus subtilis, instead of endogenous branched-chain amino acid transaminase and glutamate dehydrogenase, respectively. The yield of l-leucine reached 22.62 ± 0.17 g·L−1 by strain ΔLtbR-acetohydroxyacid isomeroreductase (AHAIR)M/ABNCME, and the concentrations of the by-products (l-valine and l-alanine) increased, compared to the strain ΔLtbR/ABNCE. Strain ΔLtbR-AHAIRMLeuDH/ABNCMLDH accumulated 22.87±0.31 g·L−1l-leucine, but showed a drastically low l-valine accumulation (from 8.06 ± 0.35 g·L−1 to 2.72 ± 0.11 g·L−1), in comparison to strain ΔLtbR-AHAIRM/ABNCME, which indicated that LeuDH has much specificity for l-leucine synthesis but not for l-valine synthesis. Subsequently, the resultant strain ΔLtbR-AHAIRMLeuDHRocG/ABNCMLDH accumulated 23.31 ± 0.24 g·L−1l-leucine with a glucose conversion efficiency of 0.191 g·g−1.
- Subjects
LEUCINE; CORYNEBACTERIUM; BIOSYNTHESIS; GLUTAMIC acid; OXIDATION-reduction reaction
- Publication
International Journal of Molecular Sciences, 2019, Vol 20, Issue 8, p2020
- ISSN
1661-6596
- Publication type
Article
- DOI
10.3390/ijms20082020