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Title: The effect of switchgrass loadings on feedstock solubilization and biofuel production by Clostridium thermocellum

High solids loading fermentations are necessary for the industrialization of lignocellulosic ethanol. To date, only a few studies have investigated the effect of solids loadings on microorganisms of interest for consolidated bioprocessing (CBP). Here, the effect that various switchgrass loadings have on Clostridium thermocellum solubilization and bioconversion are investigated. C. thermocellum was grown for ten days on 10, 25 or 50 g/L switchgrass or Avicel at equivalent glucan loadings. Avicel was completely consumed at all loadings, but total cellulose solubilization decreased from 63% to 37% as switchgrass loadings increased from 10 g/L to 50 g/L. Washed, spent switchgrass could be additionally hydrolyzed and fermented in second-round fermentations suggesting access to fermentable substrates was not the limiting factor at higher feedstock loadings. Fermentations of Avicel or cellobiose using culture medium supplemented with 50% spent fermentation broth identified that compounds present in the samples collected from the 25 or 50 g/L switchgrass loadings were the most inhibitory to continued fermentation. Finally, recalcitrance alone cannot fully account for differences in solubilization and end-production formation between switchgrass and Avicel at increased substrate loadings. Effort to decouple metabolic inhibition from inhibition of hydrolysis suggest that C. thermocellum’s hydrolytic machinery is more vulnerable to inhibition frommore » switchgrass-derived inhibitors than is the bacterium’s metabolism.« less
 [1] ;  [2] ; ORCiD logo [2]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Univ. of Calgary, Calgary, AB (Canada)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Biotechnology for Biofuels
Additional Journal Information:
Journal Volume: 10; Journal Issue: 1; Journal ID: ISSN 1754-6834
BioMed Central
Research Org:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
09 BIOMASS FUELS; Clostridium thermocellum; Consolidated bioprocessing; Switchgrass; Recalcitrance; Inhibition; High-solid loading; Ethanol
OSTI Identifier: