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Title: Consolidated bioprocessing of transgenic switchgrass by an engineered and evolved Clostridium thermocellum strain

Background: Switchgrass is an abundant and dedicated bioenergy feedstock however its inherent recalcitrance is one of the economic hurdles for producing biofuels. The down-regulation of the caffeic acid O-methyl transferase (COMT) gene in the lignin pathway of switchgrass reduced lignin content and S/G ratio, and the transgenic lines showed improved fermentation yield with S. cerevisiae and C. thermocellum (ATCC 27405) in comparison to the wild-type switchgrass. Results: Here we examine the fermentation potential of the COMT transgenic switchgrass and its wild-type line, with an engineered and evolved Clostridium thermocellum (M1570) strain. The fermentation of the transgenic switchgrass had superior conversion relative to the control line with an increase of 20% and ethanol was the primary metabolite accounting for 90% of the total metabolites measured by HPLC. Conclusions: The down-regulation of the COMT gene in switchgrass reduced recalcitrance and improved microbial bioconversion yield. Moreover, these results showed ethanol as the main fermentation metabolite produced by an engineered and evolved C. thermocellum strain grown on a transgenic switchgrass.
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  1. ORNL
  2. Noble Foundation
Publication Date:
OSTI Identifier:
DOE Contract Number:
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biotechnology for Biofuels; Journal Volume: 7; Journal Issue: 1
Research Org:
Oak Ridge National Laboratory (ORNL); BioEnergy Science Center (BESC)
Sponsoring Org:
SC USDOE - Office of Science (SC)
Country of Publication:
United States
SWITCHGRASS; CLOSTRIDIUM THERMOCELLUM; CELLULOSIC ETHANOL Transgenic; switchgrass; metabolic engineering; Clostridium thermocellum; consolidated bioprocessing; feedstock; cellulosic ethanol