Characterization of Clostridium thermocellum strains with disrupted fermentation end product pathways

Journal Article · Tue Jan 01 00:00:00 EST 2013 · Journal of Industrial Microbiology and Biotechnology

DOI:https://doi.org/10.1007/s10295-013-1275-5· OSTI ID:1083736

Van Der Veen, Douwe ^[1]; Lo, Jonathan ^[2]; Brown, Steven D ^[1]; Johnson, Courtney M ^[1]; Tschaplinski, Timothy J ^[1]; Martin, Madhavi Z ^[1]; Engle, Nancy L ^[1]; Argyros, Aaron ^[3]; Van den Berg, Robert A ^[4]; Caiazza, Nicky ^[3]; Guss, Adam M ^[1]; Lynd, Lee R ^[5]

---

1. ORNL
2. Dartmouth College
3. Mascoma Corporation
4. Katholieke University Leuven, Belgium
5. Thayer School of Engineering at Dartmouth

Clostridium thermocellum is a thermophilic, cellulolytic anaerobe that is a candidate microorganism for industrial biofuels production. Strains with mutations in genes associated with production of Llactate ( ldh) and/or acetate ( pta) were characterized to gain insight into the intracellular processes that convert cellobiose to ethanol and other fermentation end products. Cellobiose-grown cultures of the ldh strain had identical biomass accumulation, fermentation end products, transcription profile and intracellular metabolite concentrations compared to its parent strain (DSM1313 hpt spo0A). The pta-deficient strain grew slower and had 30% lower final biomass concentration compared to the parent strain, yet produced 75% more ethanol. A ldh pta double mutant strain evolved for faster growth had growth rate and ethanol yield comparable to the parent strain, whereas its biomass accumulation was comparable to pta. Free amino acids were secreted by all examined strains, with both pta strains secreting higher amounts of alanine, valine, isoleucine, proline, glutamine, and threonine. Valine concentration for ldh pta reached 5 mM by the end of growth, or 2.7% of the substrate carbon utilized. These secreted amino acid concentrations correlate with increased intracellular pyruvate concentrations, up to 6-fold in the pta and 16-fold in the ldh pta strain. We hypothesize that the deletions in fermentation end product pathways result in an intracellular redox imbalance, which the organism attempts to relieve, in part by recycling NADP+ through increased production of amino acids.

• Research Organization: Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
• Sponsoring Organization: USDOE Office of Science (SC)
• DOE Contract Number: DE-AC05-00OR22725
• OSTI ID: 1083736
• Journal Information: Journal of Industrial Microbiology and Biotechnology, Vol. 40, Issue 7; ISSN 1367-5435
• Publisher: Springer
• Country of Publication: United States
• Language: English

Related Subjects

BESC