title: Determining the roles of the three alcohol dehydrogenases (AdhA, AdhB and AdhE) in Thermoanaerobacter ethanolicus during ethanol formation.
abstract: Thermoanaerobacter ethanolicus is a promising candidate for biofuel production due to the broad range of substrates it can utilize and its high ethanol yield compared to other thermophilic bacteria, such as Clostridium thermocellum. Three alcohol dehydrogenases, AdhA, AdhB and AdhE, play key roles in ethanol formation. To study their physiological roles during ethanol formation, we deleted them separately and in combination. Previously, it has been thought that both AdhB and AdhE were bifunctional alcohol dehydrogenases. Here we show that AdhE has primarily acetyl-CoA reduction activity (ALDH) and almost no acetaldehyde reduction (ADH) activity, whereas AdhB has no ALDH activity and but high ADH activity. We found that AdhA and AdhB have similar patterns of activity. Interestingly, although deletion of both adhA and adhB reduced ethanol production, a single deletion of either one actually increased ethanol yields by 60-70%.
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, NH, USA.|Bioenergy Science Center, Oak Ridge, TN, USA.
authors.forename: Jilai
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, NH, USA.|Bioenergy Science Center, Oak Ridge, TN, USA.
authors.forename: Xiongjun
authors.initials: X
authors.lastname: Shao
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, NH, USA.|Bioenergy Science Center, Oak Ridge, TN, USA.
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Olson
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, NH, USA.|Bioenergy Science Center, Oak Ridge, TN, USA.
authors.forename: Sean Jean-Loup
authors.initials: SJ
authors.lastname: Murphy
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, NH, USA.|Bioenergy Science Center, Oak Ridge, TN, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Tian
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, NH, USA. lee.r.lynd@dartmouth.edu.|Bioenergy Science Center, Oak Ridge, TN, USA. lee.r.lynd@dartmouth.edu.
authors.forename: Lee R
authors.initials: LR
authors.lastname: Lynd
mesh_terms: D000079:Acetaldehyde / Q000378:metabolism; D000105:Acetyl Coenzyme A / Q000378:metabolism; D000426:Alcohol Dehydrogenase / Q000235:genetics / Q000378:metabolism*; D056804:Biofuels / Q000600:supply & distribution; D000431:Ethanol / Q000378:metabolism*; D046968:Thermoanaerobacter / Q000201:enzymology* / Q000235:genetics
chemical_list: D056804:Biofuels; D000431:Ethanol; D000105:Acetyl Coenzyme A; D000426:Alcohol Dehydrogenase; D000079:Acetaldehyde
keywords: Bifunctional alcohol dehydrogenase; Bioethanol; Gene deletion; Thermophilic bacteria