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

Abstract

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

Authors:
 [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:
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)
OSTI Identifier:
1413625
Grant/Contract Number:
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Biotechnology for Biofuels
Additional Journal Information:
Journal Volume: 10; Journal Issue: 1; Journal ID: ISSN 1754-6834
Publisher:
BioMed Central
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; Clostridium thermocellum; Consolidated bioprocessing; Switchgrass; Recalcitrance; Inhibition; High-solid loading; Ethanol

Citation Formats

Verbeke, Tobin J., Garcia, Gabriela M., and Elkins, James G. The effect of switchgrass loadings on feedstock solubilization and biofuel production by Clostridium thermocellum. United States: N. p., 2017. Web. doi:10.1186/s13068-017-0917-7.
Verbeke, Tobin J., Garcia, Gabriela M., & Elkins, James G. The effect of switchgrass loadings on feedstock solubilization and biofuel production by Clostridium thermocellum. United States. doi:10.1186/s13068-017-0917-7.
Verbeke, Tobin J., Garcia, Gabriela M., and Elkins, James G. Thu . "The effect of switchgrass loadings on feedstock solubilization and biofuel production by Clostridium thermocellum". United States. doi:10.1186/s13068-017-0917-7. https://www.osti.gov/servlets/purl/1413625.
@article{osti_1413625,
title = {The effect of switchgrass loadings on feedstock solubilization and biofuel production by Clostridium thermocellum},
author = {Verbeke, Tobin J. and Garcia, Gabriela M. and Elkins, James G.},
abstractNote = {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 from switchgrass-derived inhibitors than is the bacterium’s metabolism.},
doi = {10.1186/s13068-017-0917-7},
journal = {Biotechnology for Biofuels},
number = 1,
volume = 10,
place = {United States},
year = {Thu Nov 30 00:00:00 EST 2017},
month = {Thu Nov 30 00:00:00 EST 2017}
}

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  • Here, to develop and prototype a high-throughput microplate assay to assess anaerobic microorganisms and lignocellulosic biomasses in a rapid, cost-effective screen for consolidated bioprocessing potential. Clostridium thermocellum parent Δ hpt strain deconstructed Avicel to cellobiose, glucose, and generated lactic acid, formic acid, acetic acid and ethanol as fermentation products in titers and ratios similar to larger scale fermentations confirming the suitability of a plate-based method for C. thermocellum growth studies. C. thermocellum strain LL1210, with gene deletions in the key central metabolic pathways, produced higher ethanol titers in the Consolidated Bioprocessing (CBP) plate assay for both Avicel and switchgrass fermentationsmore » when compared to the Δ hpt strain. A prototype microplate assay system is developed that will facilitate high-throughput bioprospecting for new lignocellulosic biomass types, genetic variants and new microbial strains for bioethanol production.« less
  • Here, to develop and prototype a high-throughput microplate assay to assess anaerobic microorganisms and lignocellulosic biomasses in a rapid, cost-effective screen for consolidated bioprocessing potential. Clostridium thermocellum parent Δ hpt strain deconstructed Avicel to cellobiose, glucose, and generated lactic acid, formic acid, acetic acid and ethanol as fermentation products in titers and ratios similar to larger scale fermentations confirming the suitability of a plate-based method for C. thermocellum growth studies. C. thermocellum strain LL1210, with gene deletions in the key central metabolic pathways, produced higher ethanol titers in the Consolidated Bioprocessing (CBP) plate assay for both Avicel and switchgrass fermentationsmore » when compared to the Δ hpt strain. A prototype microplate assay system is developed that will facilitate high-throughput bioprospecting for new lignocellulosic biomass types, genetic variants and new microbial strains for bioethanol production.« less
  • Addition to media of yeast extract, a vitamin mixture containing vitamin B{sub 12}, biotin, pyridoxamine, and p-aminobenzoic acid, or vitamin B{sub 12} alone enhanced formation of ethanol but decreased lactate production in the fermentation of cellulose by Clostridium thermocellum I-1-B. A similar effect was not observed with C. thermocellum ATCC 27405 and JW20.
  • Here, we and others have shown the utility of long sequence reads to improve genome assembly quality. In this study, we generated PacBio DNA sequence data to improve the assemblies of draft genomes for Clostridium thermocellum AD2, Clostridium thermocellum LQRI, and Pelosinus fermentans R7.
  • We and others have shown the utility of long sequence reads to improve genome assembly quality. In this study, we generated PacBio DNA sequence data to improve the assemblies of draft genomes forClostridium thermocellumAD2,Clostridium thermocellumLQRI, andPelosinus fermentansR7.