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Title: Effects of Biomass Accessibility and Klason Lignin Contents during Consolidated Bioprocessing in Populus trichocarpa

Abstract

The bacterium Clostridium thermocellum offers a distinct and integrated approach to ethanol production through consolidated bioprocessing (CBP). The Simons’ stain technique, which assays the accessibility of lignocellulosic biomass, has been traditionally applied to fungal cellulase systems; however, its application to CBP has not been fully explored. For this reason, the structural properties of eight Populus trichocarpa with either high or low biomass densities were compared in this paper to determine bioconversion differences during separate hydrolysis and fermentation (SHF) and CBP with C. thermocellum. Simons’ staining generally identifies low density poplar as more accessible than high density poplar. Additionally, low density P. trichocarpa generally contained less Klason lignin than high density poplar. SHF and CBP treatments consistently identified BESC-7 (high density, low accessibility, low surface roughness) as a low ethanol yielding biomass and GW-9914 (low density, high accessibility, high surface roughness) as a high ethanol yielding biomass. Upon further investigation, BESC-7 also contained a high Klason lignin content (~25%), while GW-9914 had a low lignin content (~20%). Cellulose degree of polymerization (DP) measurements exhibited a weak linear correlation with accessibility (r 2 = 0.17). Finally, therefore, the ethanol yields were correlated with accessibility and lignin content extremes but not cellulose DP.

Authors:
 [1];  [2];  [2];  [3];  [3];  [3];  [2]; ORCiD logo [4]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center; Georgia Inst. of Technology, Atlanta, GA (United States). School of Chemistry and Biochemistry. Renewable BioProducts Inst.
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center. Biosciences Division. UT-ORNL Joint Inst. of Biological Science
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioSciences Division. Plant Systems Biology Group
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center. Biosciences Division. UT-ORNL Joint Inst. of Biological Science; Univ. of Tennessee, Knoxville, TN (United States). Center for Renewable Carbon. Dept. of Forestry. Dept. of Chemical and Biomolecular Engineering
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)
Contributing Org.:
Georgia Inst. of Technology, Atlanta, GA (United States); Univ. of Tennessee, Knoxville, TN (United States)
OSTI Identifier:
1362259
Grant/Contract Number:
AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
ACS Sustainable Chemistry & Engineering
Additional Journal Information:
Journal Volume: 5; Journal Issue: 6; Journal ID: ISSN 2168-0485
Publisher:
American Chemical Society (ACS)
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; Clostridium thermocellum; consolidated bioprocessing; ethanol; Klason lignin; Simons’ stain; wood density

Citation Formats

Akinosho, Hannah, Dumitrache, Alexandru, Natzke, Jace, Muchero, Wellington, Jawdy, Sara S., Tuskan, Gerald A., Brown, Steven D., and Ragauskas, Arthur J. Effects of Biomass Accessibility and Klason Lignin Contents during Consolidated Bioprocessing in Populus trichocarpa. United States: N. p., 2017. Web. doi:10.1021/acssuschemeng.7b00449.
Akinosho, Hannah, Dumitrache, Alexandru, Natzke, Jace, Muchero, Wellington, Jawdy, Sara S., Tuskan, Gerald A., Brown, Steven D., & Ragauskas, Arthur J. Effects of Biomass Accessibility and Klason Lignin Contents during Consolidated Bioprocessing in Populus trichocarpa. United States. doi:10.1021/acssuschemeng.7b00449.
Akinosho, Hannah, Dumitrache, Alexandru, Natzke, Jace, Muchero, Wellington, Jawdy, Sara S., Tuskan, Gerald A., Brown, Steven D., and Ragauskas, Arthur J. Wed . "Effects of Biomass Accessibility and Klason Lignin Contents during Consolidated Bioprocessing in Populus trichocarpa". United States. doi:10.1021/acssuschemeng.7b00449. https://www.osti.gov/servlets/purl/1362259.
@article{osti_1362259,
title = {Effects of Biomass Accessibility and Klason Lignin Contents during Consolidated Bioprocessing in Populus trichocarpa},
author = {Akinosho, Hannah and Dumitrache, Alexandru and Natzke, Jace and Muchero, Wellington and Jawdy, Sara S. and Tuskan, Gerald A. and Brown, Steven D. and Ragauskas, Arthur J.},
abstractNote = {The bacterium Clostridium thermocellum offers a distinct and integrated approach to ethanol production through consolidated bioprocessing (CBP). The Simons’ stain technique, which assays the accessibility of lignocellulosic biomass, has been traditionally applied to fungal cellulase systems; however, its application to CBP has not been fully explored. For this reason, the structural properties of eight Populus trichocarpa with either high or low biomass densities were compared in this paper to determine bioconversion differences during separate hydrolysis and fermentation (SHF) and CBP with C. thermocellum. Simons’ staining generally identifies low density poplar as more accessible than high density poplar. Additionally, low density P. trichocarpa generally contained less Klason lignin than high density poplar. SHF and CBP treatments consistently identified BESC-7 (high density, low accessibility, low surface roughness) as a low ethanol yielding biomass and GW-9914 (low density, high accessibility, high surface roughness) as a high ethanol yielding biomass. Upon further investigation, BESC-7 also contained a high Klason lignin content (~25%), while GW-9914 had a low lignin content (~20%). Cellulose degree of polymerization (DP) measurements exhibited a weak linear correlation with accessibility (r2 = 0.17). Finally, therefore, the ethanol yields were correlated with accessibility and lignin content extremes but not cellulose DP.},
doi = {10.1021/acssuschemeng.7b00449},
journal = {ACS Sustainable Chemistry & Engineering},
number = 6,
volume = 5,
place = {United States},
year = {Wed Apr 26 00:00:00 EDT 2017},
month = {Wed Apr 26 00:00:00 EDT 2017}
}

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  • Because cellulosic ethanol production remains cost-prohibitive„ advances in consolidated bioprocessing (CBP) have been directed towards lifting this restriction. CBP reduces the need for added enzymes and can potentially slash ethanol production costs through process integration. Clostridium thermocellum, a CBP microorganism, organizes its enzymes in a multi-enzyme complex - a stark contrast to fungal enzymes. Nonetheless, recalcitrance may limit the extent of biomass deconstruction. Here in this study, six Populus were treated with C. thermocellum (ATCC 27405) and characterized to determine structural changes that resulted from CBP. The 2D HSQC NMR spectra of lignin-enriched residues revealed that higher S/G ratio (2.6)more » and fewer carbon-carbon interunit linkages (generally 2–5%) were present in the top performing poplar. Furthermore, cellulose degree of polymerization data suggests that C. thermocellum likely circumvents long chain cellulose, while cellulose crystallinity and hemicellulose molecular weight data do not provide a direct indication of features connected to recalcitrance. Hence, C. thermocellum is similarly impacted by the proposed lignin properties that negatively impact biomass deconstruction using fungal enzymes.« less
  • During consolidated bioprocessing (CBP), Clostridium thermocellum hydrolyzes several plant cell wall components. Cellulose hydrolysis, specifically, liberates sugars for fermentation, which generates ethanol, acetate, hydrogen, and other products. While several studies indicate that C. thermocellum hydrolyzes carbohydrates in biomass, the structural changes to lignin during CBP remain unclear. In this paper, the whole plant cell walls of untreated and C. thermocellum-treated Populus trichocarpa were characterized using NMR and FTIR. The results suggest that C. thermocellum reduces the β-O-4 linkage content and increases the lignin S/G ratio. Finally, this investigation indicates that C. thermocellum not only modifies lignin in order to accessmore » cellulose but also leaves behind a suitable lignin substrate for value-added applications in the cellulosic ethanol production scheme.« less
  • Lignin S/G ratio has been investigated as an important factor in biomass recalcitrance to bioethanol production. Because of the complexity and variety of biomass, recalcitrance was also reportedly influenced by several other factors, such as total lignin content, degree of cellulose polymerization, etc. In addition, the effect of S/G ratio on biomass conversion is not uniform across plant species. Herein, 11 Populus trichocarpa natural variants grown under the same conditions with similar total lignin content were selected to minimize the effects of other factors. The lignin S/G ratio of the selected P. trichocarpa natural variants showed negative correlations with p-hydroxybenzoatemore » (PB) and β–5 linkage contents, while it had positive ones with β-O-4 linkage, lignin molecular weight, and ethanol production. In conclusion, this study showed the importance of lignin S/G ratio as an independent recalcitrance factor that may aid future energy crop engineering and biomass conversion strategies.« less
  • Lignin S/G ratio has been investigated as an important factor in biomass recalcitrance to bioethanol production. Because of the complexity and variety of biomass, recalcitrance was also reportedly influenced by several other factors, such as total lignin content, degree of cellulose polymerization, etc. In addition, the effect of S/G ratio on biomass conversion is not uniform across plant species. Herein, 11 Populus trichocarpa natural variants grown under the same conditions with similar total lignin content were selected to minimize the effects of other factors. The lignin S/G ratio of the selected P. trichocarpa natural variants showed negative correlations with p-hydroxybenzoatemore » (PB) and ..beta..-5 linkage contents, while it had positive ones with ..beta..-O-4 linkage, lignin molecular weight, and ethanol production. This study showed the importance of lignin S/G ratio as an independent recalcitrance factor that may aid future energy crop engineering and biomass conversion strategies.« less