title: Identification of acetoin reductases involved in 2,3-butanediol pathway in Klebsiella oxytoca.
abstract: The acetoin reductase (AR) of Klebsiella oxytoca is responsible for converting acetoin into 2,3-butanediol (2,3-BDO) during sugar fermentation. Deleting the AR encoding gene (budC) in the 2,3-BDO operon does not block production of 2,3-BDO, as another similar gene exists in addition to budC called diacetyl/acetoin reductase (dar) which shares 53% identity with budC. In the present study, both budC and dar of K. oxytoca were independently cloned and expressed in Escherichia coli along with budA (acetolactate decarboxylase) and budB (acetolactate synthase), which are responsible for converting pyruvate into acetoin. The recombinant E. coli expressing budABC and budAB-dar produced 2,3-BDO from glucose but E. coli expressing only budAB did not and produced acetoin alone. This demonstrates that Dar functions similar to BudC. Mutants of budC, dar, and both genes together were developed in K. oxytoca ΔldhA (lactate dehydrogenase). K. oxytoca ΔldhA ΔbudC Δdar, deficient in both AR genes, showed reduced 2,3-BDO concentration when compared to K. oxytoca ΔldhA and K. oxytoca ΔldhA ΔbudC by 84% and 69%, respectively. Interestingly, K. oxytoca ΔldhA Δdar resulted in a significant reduction in the reversible conversion of 2,3-BDO into acetoin than that of K. oxytoca ΔldhA, which was observed in a glucose depleted fermentation culture. In addition, we observed that Dar played a key role in dissimilation of 2,3-BDO in media containing 2,3-BDO alone.
authors.affiliation: R&D Center, GS Caltex Corporation, 104-4 Munji-dong, Yusung-gu, Daejeon 305-380, Republic of Korea. Electronic address: aprilkenzo@kaist.ac.kr.
authors.forename: Taek Ho
authors.initials: TH
authors.lastname: Yang
authors.affiliation: R&D Center, GS Caltex Corporation, 104-4 Munji-dong, Yusung-gu, Daejeon 305-380, Republic of Korea.
authors.forename: Chelladurai
authors.initials: C
authors.lastname: Rathnasingh
authors.affiliation: R&D Center, GS Caltex Corporation, 104-4 Munji-dong, Yusung-gu, Daejeon 305-380, Republic of Korea.
authors.forename: Hee Jong
authors.initials: HJ
authors.lastname: Lee
authors.affiliation: R&D Center, GS Caltex Corporation, 104-4 Munji-dong, Yusung-gu, Daejeon 305-380, Republic of Korea.
authors.forename: Doyoung
authors.initials: D
authors.lastname: Seung
mesh_terms: D000093:Acetoin / Q000378:metabolism*; D000095:Acetolactate Synthase / Q000235:genetics / Q000378:metabolism; D000429:Alcohol Oxidoreductases / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D002072:Butylene Glycols / Q000378:metabolism*; D002262:Carboxy-Lyases / Q000235:genetics / Q000378:metabolism; D003001:Cloning, Molecular; D005285:Fermentation; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D041121:Klebsiella oxytoca / Q000166:cytology* / Q000235:genetics; D019289:Pyruvic Acid / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D002072:Butylene Glycols; C026978:2,3-butylene glycol; D019289:Pyruvic Acid; D000093:Acetoin; D000429:Alcohol Oxidoreductases; C019801:butanediol dehydrogenase; D000095:Acetolactate Synthase; D002262:Carboxy-Lyases; C023746:acetolactate decarboxylase
keywords: 2,3-Butanediol pathway; Acetoin reductase; Butanediol dehydrogenase; Klebsiella oxytoca