Improvement of l-Leucine Production in Corynebacterium glutamicum by Altering the Redox Flux

International Journal of Molecular Sciences

Xiu-Lai Chen¹  Li-Ming Liu¹  Jian-Zhong Xu²  Wei-Guo Zhang²  Feng Zhang²  Ying-Yu Wang² 

[1] State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China;The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800 Lihu Road, Wuxi 214122, China;

关键词: Corynebacterium glutamicum;    l-leucine;    acetohydroxyacid isomeroreductase;    leucine dehydrogenase;    NAD-dependent glutamate dehydrogenase;   

DOI  :  10.3390/ijms20082020

来源: DOAJ

【 摘 要 】

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/ABNC^ME, and the concentrations of the by-products (l-valine and l-alanine) increased, compared to the strain ΔLtbR/ABNCE. Strain ΔLtbR-AHAIR^MLeuDH/ABNC^MLDH accumulated 22.87±0.31 g·L⁻¹ l-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-AHAIR^M/ABNC^ME, which indicated that LeuDH has much specificity for l-leucine synthesis but not for l-valine synthesis. Subsequently, the resultant strain ΔLtbR-AHAIR^MLeuDHRocG/ABNC^MLDH accumulated 23.31 ± 0.24 g·L⁻¹ l-leucine with a glucose conversion efficiency of 0.191 g·g⁻¹.

【 授权许可】

Unknown