title: Engineered Expression Vectors Significantly Enhanced the Production of 2-Keto-D-gluconic Acid by Gluconobacter oxidans.
abstract: 2-Keto-D-gluconic acid (2KGA), a precursor of the important food antioxidant erythorbic acid, can be produced by Gluconobacter oxidans. To genetically engineer G. oxidans for improved 2KGA production, six new expression vectors with increased copy numbers based on pBBR1MCS-5 were constructed via rational mutagenesis. The utility of the mutant vectors was demonstrated by the increased ga2dh mRNA abundance, enzyme activity, and 2KGA production when the ga2dh gene was overexpressed using these vectors. Among the obtained constructs, G. oxidans/pBBR-3510-ga2dh displayed the highest oxidative activity toward gluconic acid (GA). In a batch biotransformation process, the G. oxidans/pBBR-3510-ga2dh strain exhibited 2KGA productivity (0.63 g/g CWW/h) higher than that obtained using strain G. oxidans/pBBR-ga2dh (0.40 g/g CWW/h). When sufficient oxygen was supplied during the biotransformation, up to 480 g/L GA was exhausted in 45 h by the G. oxidans/pBBR-3510-ga2dh strain and approximately 486 g/L 2KGA was produced, generating the productivity of 0.54 g/g CWW/h.
authors.affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China.
authors.forename: Yuan-yuan
authors.initials: YY
authors.lastname: Shi
authors.affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China.
authors.forename: Ke-fei
authors.initials: KF
authors.lastname: Li
authors.affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China.
authors.forename: Jin-ping
authors.initials: JP
authors.lastname: Lin
authors.affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China.
authors.forename: Sheng-li
authors.initials: SL
authors.lastname: Yang
authors.affiliation: State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, China.
authors.forename: Dong-zhi
authors.initials: DZ
authors.lastname: Wei
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002237:Carbohydrate Dehydrogenases / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D005818:Genetic Engineering; D005822:Genetic Vectors / Q000235:genetics* / Q000378:metabolism; D005942:Gluconates / Q000378:metabolism*; D020600:Gluconobacter oxydans / Q000235:genetics* / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D005942:Gluconates; D002237:Carbohydrate Dehydrogenases; C030691:gluconic acid
keywords: 2-keto-d-gluconic acid; Gluconobacter oxidans; expression vectors; overexpression; plasmid copy number