title: Constructing a synthetic constitutive metabolic pathway in Escherichia coli for (R, R)-2,3-butanediol production.
abstract: Many microorganisms could naturally produce (R, R)-2,3-butanediol ((R, R)-2,3-BD), which has unique applications due to its special chiral group and spatial configuration. But the low enantio-purity of the product hindered the development of large-scale production. In this work, a synthetic constitutive metabolic pathway for enantiomerically pure (R, R)-2,3-BD biosynthesis was constructed in Escherichia coli with vector pUC6S, which does not contain any lac sequences. The expression of this artificial constructed gene cluster was optimized by using two different strength of promoters (AlperPLTet01 (P01) and AlperBB (PBB)). The strength of P01 is twice stronger than PBB. The fermentation results suggested that the yield of (R, R)-2,3-BD was higher when using the stronger promoter. Compared with the wild type, the recombinant strain E. coli YJ2 produced a small amount of acetic acid and showed higher glucose consumption rate and higher cell density, which indicated a protection against acetic acid inhibition. In order to further increase the (R, R)-2,3-BD production by reducing the accumulation of its precursor acetoin, the synthetic operon was reconstructed by adding the strong promoter P01 in front of the gene ydjL coding for the enzyme of (R, R)-2,3-BD dehydrogenase which catalyzes the conversion of acetoin to (R, R)-2,3-BD. The engineered strain E. coli YJ3 showed a 20 % decrease in acetoin production compared with that of E. coli YJ2. After optimization the fermentation conditions, 30.5 g/L of (R, R)-2,3-BD and 3.2 g/L of acetoin were produced from 80 g/L of glucose within 18 h, with an enantio-purity over 99 %.
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, No. 30 South Puzhu Road, Nanjing, 211816, People's Republic of China.
authors.forename: Ying-Jia
authors.initials: YJ
authors.lastname: Tong
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, No. 30 South Puzhu Road, Nanjing, 211816, People's Republic of China. xiaojunji@njtech.edu.cn.
authors.forename: Xiao-Jun
authors.identifier: http://orcid.org/0000-0002-6450-0229
authors.initials: XJ
authors.lastname: Ji
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, No. 30 South Puzhu Road, Nanjing, 211816, People's Republic of China.
authors.forename: Meng-Qiu
authors.initials: MQ
authors.lastname: Shen
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, No. 30 South Puzhu Road, Nanjing, 211816, People's Republic of China.
authors.forename: Lu-Gang
authors.initials: LG
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, No. 30 South Puzhu Road, Nanjing, 211816, People's Republic of China.
authors.forename: Zhi-Kui
authors.initials: ZK
authors.lastname: Nie
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering, College of Biotechnology and Pharmaceutical Engineering, Nanjing Tech University, No. 30 South Puzhu Road, Nanjing, 211816, People's Republic of China. biotech@njtech.edu.cn.
authors.forename: He
authors.initials: H
authors.lastname: Huang
mesh_terms: D000093:Acetoin / Q000378:metabolism; D061249:Batch Cell Culture Techniques; D002072:Butylene Glycols / Q000378:metabolism*; D004926:Escherichia coli / Q000235:genetics* / Q000378:metabolism*; D005285:Fermentation; D005947:Glucose / Q000378:metabolism; D007763:Lac Operon; D060847:Metabolic Engineering / Q000379:methods; D053858:Metabolic Networks and Pathways / Q000235:genetics; D005810:Multigene Family; D011401:Promoter Regions, Genetic; D058615:Synthetic Biology / Q000379:methods
chemical_list: D002072:Butylene Glycols; C026978:2,3-butylene glycol; D000093:Acetoin; D005947:Glucose
keywords: (R, R)-2,3-butanediol; Escherichia coli; Metabolic engineering; Promoter