title: BothadhEand a Separate NADPH-Dependent Alcohol Dehydrogenase Gene,adhA, Are Necessary for High Ethanol Production in Thermoanaerobacterium saccharolyticum.
abstract: Thermoanaerobacterium saccharolyticumhas been engineered to produce ethanol at about 90% of the theoretical maximum yield (2 ethanol molecules per glucose equivalent) and a titer of 70 g/liter. Its ethanol-producing ability has drawn attention to its metabolic pathways, which could potentially be transferred to other organisms of interest. Here, we report that the iron-containing AdhA is important for ethanol production in the high-ethanol strain ofT. saccharolyticum(LL1049). A single-gene deletion ofadhAin LL1049 reduced ethanol production by ∼50%, whereas multiple gene deletions of all annotated alcohol dehydrogenase genes exceptadhAandadhEdid not affect ethanol production. Deletion ofadhAin wild-typeT.saccharolyticumreduced NADPH-linked alcohol dehydrogenase (ADH) activity (acetaldehyde-reducing direction) by 93%.IMPORTANCEIn this study, we set out to identify the alcohol dehydrogenases necessary for high ethanol production inT. saccharolyticumBased on previous work, we had assumed thatadhEwas the primary alcohol dehydrogenase gene. Here, we show that bothadhAandadhEare needed for high ethanol yield in the engineered strain LL1049. This is the first report showingadhAis important for ethanol production in a nativeadhAhost, which has important implications for achieving higher ethanol yields in other microorganisms.
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA.|BioEnergy Science Center, Oak Ridge, Tennessee, USA.
authors.forename: Tianyong
authors.initials: T
authors.lastname: Zheng
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA.|BioEnergy Science Center, Oak Ridge, Tennessee, USA.
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Olson
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA.|BioEnergy Science Center, Oak Ridge, Tennessee, USA.
authors.forename: Sean J
authors.initials: SJ
authors.lastname: Murphy
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA.|BioEnergy Science Center, Oak Ridge, Tennessee, USA.
authors.forename: Xiongjun
authors.initials: X
authors.lastname: Shao
authors.affiliation: Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA.|BioEnergy Science Center, Oak Ridge, Tennessee, USA.
authors.forename: Liang
authors.initials: L
authors.lastname: Tian
authors.affiliation: Department of Biological Sciences, Dartmouth College, Hanover, New Hampshire, USA Lee.R.Lynd@Dartmouth.edu.|Thayer School of Engineering, Dartmouth College, Hanover, New Hampshire, USA.|BioEnergy Science Center, Oak Ridge, Tennessee, USA.
authors.forename: Lee R
authors.initials: LR
authors.lastname: Lynd
keywords: AdhA; Thermoanaerobacterium saccharolyticum; alcohol dehydrogenase; biofuel; ethanol