| Autor: |
Wang YY; The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800# Lihu Road, Wuxi 214122, China. wangyy0711@163.com., Zhang F; The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800# Lihu Road, Wuxi 214122, China. zhang20180606@sina.com., Xu JZ; The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800# Lihu Road, Wuxi 214122, China. xujianzhong@jiangnan.edu.cn.; The Key Laboratory of Carbohydrate Chemistry and Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800# Lihu Road, Wuxi 214122, China. xujianzhong@jiangnan.edu.cn., Zhang WG; The Key Laboratory of Industrial Biotechnology, Ministry of Education, School of Biotechnology, Jiangnan University, 1800# Lihu Road, Wuxi 214122, China. zhangwg168@163.com., Chen XL; State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China. shirleyl1205@163.com., Liu LM; State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China. peidongchen13@163.com. |
| Abstrakt: |
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 M E, and the concentrations of the by-products (l-valine and l-alanine) increased, compared to the strain ΔLtbR/ABNCE. Strain ΔLtbR-AHAIR M LeuDH/ABNC M LDH 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 M E, which indicated that LeuDH has much specificity for l-leucine synthesis but not for l-valine synthesis. Subsequently, the resultant strain ΔLtbR-AHAIR M LeuDHRocG/ABNC M LDH accumulated 23.31 ± 0.24 g·L -1 l-leucine with a glucose conversion efficiency of 0.191 g·g -1 . |
