title: Attenuating l-lysine production by deletion of ddh and lysE and their effect on l-threonine and l-isoleucine production in Corynebacterium glutamicum.
abstract: The fermentative production of l-threonine and l-isoleucine with Corynebacterium glutamicum is usually accompanied by the by-production of l-lysine, which shares partial biosynthesis pathway with l-threonine and l-isoleucine. Since the direct precursor for l-lysine synthesis, diaminopimelate, is a component of peptidoglycan and thus essential for cell wall synthesis, reducing l-lysine by-production could be troublesome. Here, a basal strain with eliminated l-lysine production was constructed from the wild type C. glutamicum ATCC13869 by deleting the chromosomal ddh and lysE. Furthermore, the basal strain as well as the ddh single mutant strain was engineered for l-threonine production by over-expressing lysC1, hom1 and thrB, and for l-isoleucine production by over-expressing lysC1, hom1, thrB and ilvA1. Fermentation experiments with the engineered strains showed that (i) deletion of ddh improved l-threonine production by 17%, and additional deletion of lysE further improved l-threonine production by 28%; (ii) deletion of ddh improved l-isoleucine production by 8% and improved cell growth by 21%, whereas additional deletion of lysE had no further influence on both l-isoleucine production and cell growth; (iii) l-lysine by-production was reduced by 95% and 86% in l-threonine and l-isoleucine production, respectively, by deletion of ddh and lysE. This is the first report on improving l-threonine and l-isoleucine production by deleting ddh and lysE in C. glutamicum. The results demonstrate deletion of ddh and lysE as an effective strategy to reduce l-lysine by-production without surrendering the cell growth of C. glutamicum.
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China; Key Laboratory of Industrial Biotechnology of Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China.
authors.forename: Xunyan
authors.initials: X
authors.lastname: Dong
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China; Key Laboratory of Industrial Biotechnology of Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China.
authors.forename: Yue
authors.initials: Y
authors.lastname: Zhao
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China; Key Laboratory of Industrial Biotechnology of Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China.
authors.forename: Jinyu
authors.initials: J
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China; Key Laboratory of Industrial Biotechnology of Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China.
authors.forename: Ye
authors.initials: Y
authors.lastname: Li
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi 214122, China; Key Laboratory of Industrial Biotechnology of Ministry of Education, School of Biotechnology, Jiangnan University, Wuxi 214122, China; Synergetic Innovation Center of Food Safety and Nutrition, Jiangnan University, Wuxi, China. Electronic address: xiaoyuanwang@hotmail.com.
authors.forename: Xiaoyuan
authors.initials: X
authors.lastname: Wang
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D026923:Amino Acid Transport Systems, Basic / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D053898:Biosynthetic Pathways; D048230:Corynebacterium glutamicum / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D005285:Fermentation; D017353:Gene Deletion; D005798:Genes, Bacterial; D007532:Isoleucine / Q000096:biosynthesis*; D008239:Lysine / Q000096:biosynthesis*; D060847:Metabolic Engineering; D013912:Threonine / Q000096:biosynthesis*
chemical_list: D026923:Amino Acid Transport Systems, Basic; D001426:Bacterial Proteins; C104616:LysE protein, Corynebacterium glutamicum; D007532:Isoleucine; D013912:Threonine; D000594:Amino Acid Oxidoreductases; C020032:diaminopimelate dehydrogenase; D008239:Lysine
keywords: Corynebacterium glutamicum; Metabolic engineering; l-isoleucine biosynthesis; l-lysine by-production; l-threonine biosynthesis