title: Engineering Corynebacterium glutamicum for violacein hyper production.
abstract: BACKGROUND
  Corynebacterium glutamicum was used as a metabolic engineering chassis for production of crude violacein (mixture of violacein and deoxyviolacein) due to Corynebacterium's GRAS status and advantages in tryptophan fermentation. The violacein is a commercially potential compound with various applications derived from L-tryptophan.
  
  
  RESULTS
  Corynebacterium glutamicum ATCC 21850 that could produce 162.98 mg L(-1) tryptophan was employed as a novel host for metabolic engineering chassis. Heterologous vio operon from Chromobacterium violaceum was over-expressed in ATCC 21850 strain with constitutive promoter to have obtained 532 mg L(-1) violacein. Considering toxicity of violacein, vio operon was expressed with inducible promoter and 629 mg L(-1) violacein was obtained in batch culture. Due to the economical coding nature of vio operon, the compressed RBS of vio genes were replaced with complete strong C. glutamicum ones. And extended expression units were assembled to form a synthetic operon. With this strategy, 1116 mg L(-1) violacein in batch culture was achieved. Fermentation process was then optimized by studying induction time, induction concentration, culture composition and fermentation temperature. as a result, a titer of 5436 mg L(-1) and a productivity of 47 mg L(-1) h(-1) were achieved in 3 L bioreactor.
  
  
  CONCLUSIONS
  With metabolic engineering and fermentation optimization practice, C. glutamicum 21850 (pEC-C-vio1) was able to produce violacein with both titer and productivity at the highest level ever reported. Due to advantages of mature C. glutamicum fermentation industry, this work has built basis for commercial production of violacein.
authors.affiliation: School of Biological Engineering, Dalian Polytechnic University, Dalian, 116034, People's Republic of China.
authors.forename: Hongnian
authors.initials: H
authors.lastname: Sun
authors.affiliation: Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China.
authors.forename: Dongdong
authors.initials: D
authors.lastname: Zhao
authors.affiliation: Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China.
authors.forename: Bin
authors.initials: B
authors.lastname: Xiong
authors.affiliation: School of Biological Engineering, Dalian Polytechnic University, Dalian, 116034, People's Republic of China. zhangcz@dlpu.edu.cn.
authors.forename: Chunzhi
authors.initials: C
authors.lastname: Zhang
authors.affiliation: Tianjin Institute of Industrial Biotechnology, Chinese Academy of Sciences, Tianjin, 300308, People's Republic of China. bi_ch@tib.cas.cn.
authors.forename: Changhao
authors.identifier: http://orcid.org/0000-0002-1940-8511
authors.initials: C
authors.lastname: Bi
mesh_terms: D061249:Batch Cell Culture Techniques; D019149:Bioreactors; D002861:Chromobacterium / Q000235:genetics; D048230:Corynebacterium glutamicum / Q000235:genetics* / Q000378:metabolism*; D004926:Escherichia coli; D005285:Fermentation; D007211:Indoles / Q000378:metabolism*; D007218:Industrial Microbiology / Q000379:methods; D060847:Metabolic Engineering / Q000379:methods*; D009876:Operon; D014364:Tryptophan / Q000378:metabolism
chemical_list: D007211:Indoles; D014364:Tryptophan; C063155:violacein
keywords: Corynebacterium glutamicum; L-Tryptophan; Metabolic engineering; Violacein