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Title: Elimination of formate production in Clostridium thermocellum

We study the ability of Clostridium thermocellum to rapidly degrade cellulose and ferment resulting hydrolysis products into ethanol makes it a promising platform organism for cellulosic biofuel production via consolidated bioprocessing. Currently, however, ethanol yield are far below theoretical maximum due to branched product pathways that divert carbon and electrons towards formate, H2, lactate, acetate, and secreted amino acids. To redirect carbon and electron flux away from formate, pyruvate:formate lyase (pfl) and respective PFL-activating enzyme were deleted. Formate production in the resulting Δpfl strain was eliminated and acetate production decreased by 50% on both complex and defined medium. Growth rate of Δpfl decreased by 2.9-fold on defined medium and diauxic growth was observed on complex medium. Supplementation of defined medium with 2 mM formate restored Δpfl growth rate to 80% of the parent strain. Finally, we discuss the role of pfl in metabolic engineering strategies and C1 metabolism.
 [1] ;  [2] ;  [1]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); ; Dartmouth College, Hanover, NH (United States)
Publication Date:
OSTI Identifier:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Journal of Industrial Microbiology and Biotechnology
Additional Journal Information:
Journal Volume: 42; Journal Issue: 9; Journal ID: ISSN 1367-5435
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
09 BIOMASS FUELS; 59 BASIC BIOLOGICAL SCIENCES Cellulosic ethanol; Clostridium thermocellum; Pyruvate:formate lyase; Metabolic engineering; C1 metabolism