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Title: Multiple levers for overcoming the recalcitrance of lignocellulosic biomass

Abstract

The recalcitrance of cellulosic biomass is widely recognized as a key barrier to cost-effective biological processing to fuels and chemicals, but the relative impacts of physical, chemical and genetic interventions to improve biomass processing singly and in combination have yet to be evaluated systematically. Solubilization of plant cell walls can be enhanced by non-biological augmentation including physical cotreatment and thermochemical pretreatment, the choice of biocatalyst, the choice of plant feedstock, genetic engineering of plants, and choosing feedstocks that are less recalcitrant natural variants. A two-tiered combinatoric investigation of lignocellulosic biomass deconstruction was undertaken with three biocatalysts (Clostridium thermocellum, Caldicellulosiruptor bescii, Novozymes Cellic(R) Ctec2 and Htec2), three transgenic switchgrass plant lines (COMT, MYB4, GAUT4) and their respective nontransgenic controls, two Populus natural variants, and augmentation of biological attack using either mechanical cotreatment or cosolvent-enhanced lignocellulosic fractionation (CELF) pretreatment. In the absence of augmentation and under the conditions tested, increased total carbohydrate solubilization (TCS) was observed for 8 of the 9 combinations of switchgrass modifications and biocatalysts tested, and statistically significant for five of the combinations. Here, our results indicate that recalcitrance is not a trait determined by the feedstock only, but instead is coequally determined by the choice of biocatalyst. TCSmore » with C. thermocellum was significantly higher than with the other two biocatalysts. Both CELF pretreatment and cotreatment via continuous ball milling enabled TCS in excess of 90%. Based on our results as well as literature studies, it appears that some form of non-biological augmentation will likely be necessary for the foreseeable future to achieve high TCS for most cellulosic feedstocks. However, our results show that this need not necessarily involve thermochemical processing, and need not necessarily occur prior to biological conversion. Under the conditions tested, the relative magnitude of TCS increase was augmentation > biocatalyst choice > plant choice > plant modification > plant natural variants. In the presence of augmentation, plant modification, plant natural variation, and plant choice exhibited a small, statistically non-significant impact on TCS.« less

Authors:
 [1];  [1];  [2];  [3];  [4];  [5];  [5];  [6];  [7];  [7];  [8];  [9];  [9];  [4];  [4];  [2];  [10];  [10];  [10];  [2] more »;  [4];  [1] « less
  1. Dartmouth College, Hanover, NH (United States). Thayer School of Engineering; Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC). Bourns College of Engineering, Dept. of Chemical and Environmental Engineering and Center for Environmental Research and Technology
  3. Dartmouth College, Hanover, NH (United States). Thayer School of Engineering
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC) and Biosciences Division
  5. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC); Noble Research Inst. Ardmore, OK (United States). Genomics Division
  6. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC); Univ. of North Texas, Denton, TX (United States). Dept. of Biological Sciences
  7. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC); Univ. of Georgia, Athens, GA (United States). Complex Carbohydrate Research Center
  8. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC) ; Noble Research Inst. Ardmore, OK (United States). Genomics Division
  9. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC); Univ. of Tennessee, Knoxville, TN (United States). Dept. of Plant Sciences
  10. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC); National Renewable Energy Lab. (NREL), Golden, CO (United States). Bioenergy Science and Technology
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States); 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:
1493693
Alternate Identifier(s):
OSTI ID: 1501677
Report Number(s):
NREL/JA-2700-73226
Journal ID: ISSN 1754-6834
Grant/Contract Number:  
AC36-08GO28308; AC05-00OR22725
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Biotechnology for Biofuels
Additional Journal Information:
Journal Volume: 12; Journal Issue: 1; Journal ID: ISSN 1754-6834
Publisher:
BioMed Central
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; biomass deconstruction; recalcitrance; transgenic switchgrass; Populus natural variants; Clostridium thermocellum; Caldicellulosiruptor bescii; cotreatment; CELF; fungal cellulase

Citation Formats

Holwerda, Evert K., Worthen, Robert S., Kothari, Ninad, Lasky, Ronald C., Davison, Brian H., Fu, Chunxiang, Wang, Zeng-Yu, Dixon, Richard A., Biswal, Ajaya K., Mohnen, Debra, Nelson, Richard S., Baxter, Holly L., Mazarei, Mitra, Muchero, Wellington, Tuskan, Gerald A., Cai, Charles M., Gjersing, Erica E., Davis, Mark F., Himmel, Michael E., Wyman, Charles E., Gilna, Paul, and Lynd, Lee R. Multiple levers for overcoming the recalcitrance of lignocellulosic biomass. United States: N. p., 2019. Web. doi:10.1186/s13068-019-1353-7.
Holwerda, Evert K., Worthen, Robert S., Kothari, Ninad, Lasky, Ronald C., Davison, Brian H., Fu, Chunxiang, Wang, Zeng-Yu, Dixon, Richard A., Biswal, Ajaya K., Mohnen, Debra, Nelson, Richard S., Baxter, Holly L., Mazarei, Mitra, Muchero, Wellington, Tuskan, Gerald A., Cai, Charles M., Gjersing, Erica E., Davis, Mark F., Himmel, Michael E., Wyman, Charles E., Gilna, Paul, & Lynd, Lee R. Multiple levers for overcoming the recalcitrance of lignocellulosic biomass. United States. doi:10.1186/s13068-019-1353-7.
Holwerda, Evert K., Worthen, Robert S., Kothari, Ninad, Lasky, Ronald C., Davison, Brian H., Fu, Chunxiang, Wang, Zeng-Yu, Dixon, Richard A., Biswal, Ajaya K., Mohnen, Debra, Nelson, Richard S., Baxter, Holly L., Mazarei, Mitra, Muchero, Wellington, Tuskan, Gerald A., Cai, Charles M., Gjersing, Erica E., Davis, Mark F., Himmel, Michael E., Wyman, Charles E., Gilna, Paul, and Lynd, Lee R. Thu . "Multiple levers for overcoming the recalcitrance of lignocellulosic biomass". United States. doi:10.1186/s13068-019-1353-7. https://www.osti.gov/servlets/purl/1493693.
@article{osti_1493693,
title = {Multiple levers for overcoming the recalcitrance of lignocellulosic biomass},
author = {Holwerda, Evert K. and Worthen, Robert S. and Kothari, Ninad and Lasky, Ronald C. and Davison, Brian H. and Fu, Chunxiang and Wang, Zeng-Yu and Dixon, Richard A. and Biswal, Ajaya K. and Mohnen, Debra and Nelson, Richard S. and Baxter, Holly L. and Mazarei, Mitra and Muchero, Wellington and Tuskan, Gerald A. and Cai, Charles M. and Gjersing, Erica E. and Davis, Mark F. and Himmel, Michael E. and Wyman, Charles E. and Gilna, Paul and Lynd, Lee R.},
abstractNote = {The recalcitrance of cellulosic biomass is widely recognized as a key barrier to cost-effective biological processing to fuels and chemicals, but the relative impacts of physical, chemical and genetic interventions to improve biomass processing singly and in combination have yet to be evaluated systematically. Solubilization of plant cell walls can be enhanced by non-biological augmentation including physical cotreatment and thermochemical pretreatment, the choice of biocatalyst, the choice of plant feedstock, genetic engineering of plants, and choosing feedstocks that are less recalcitrant natural variants. A two-tiered combinatoric investigation of lignocellulosic biomass deconstruction was undertaken with three biocatalysts (Clostridium thermocellum, Caldicellulosiruptor bescii, Novozymes Cellic(R) Ctec2 and Htec2), three transgenic switchgrass plant lines (COMT, MYB4, GAUT4) and their respective nontransgenic controls, two Populus natural variants, and augmentation of biological attack using either mechanical cotreatment or cosolvent-enhanced lignocellulosic fractionation (CELF) pretreatment. In the absence of augmentation and under the conditions tested, increased total carbohydrate solubilization (TCS) was observed for 8 of the 9 combinations of switchgrass modifications and biocatalysts tested, and statistically significant for five of the combinations. Here, our results indicate that recalcitrance is not a trait determined by the feedstock only, but instead is coequally determined by the choice of biocatalyst. TCS with C. thermocellum was significantly higher than with the other two biocatalysts. Both CELF pretreatment and cotreatment via continuous ball milling enabled TCS in excess of 90%. Based on our results as well as literature studies, it appears that some form of non-biological augmentation will likely be necessary for the foreseeable future to achieve high TCS for most cellulosic feedstocks. However, our results show that this need not necessarily involve thermochemical processing, and need not necessarily occur prior to biological conversion. Under the conditions tested, the relative magnitude of TCS increase was augmentation > biocatalyst choice > plant choice > plant modification > plant natural variants. In the presence of augmentation, plant modification, plant natural variation, and plant choice exhibited a small, statistically non-significant impact on TCS.},
doi = {10.1186/s13068-019-1353-7},
journal = {Biotechnology for Biofuels},
issn = {1754-6834},
number = 1,
volume = 12,
place = {United States},
year = {2019},
month = {1}
}

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Figures / Tables:

Fig. 1 Fig. 1: Fractional total carbohydrate solubilization for three transgenic switchgrass lines and their controls mediated by three different biocatalysts. Fungal cellulase was loaded at 5 mg/g solids and in a 9:1 ratio for Ctec2 and Htec2. Red bars show solubilization for the control plant lines (−) and blue bars showmore » solubilization for the transgenic switchgrass lines (+). Initial solids concentrations were based on equal glucan loadings, and fermentations were done in duplicate. Solubilization results are after 120 h of incubation. Error bars represent one standard deviation and are based on biological replicates. Both COMT and MYB4 represent modifications in the lignin pathway, and GAUT4 represents modification in the pectin pathway. An asterisk (*) indicates that the difference in solubilization between transgenic and control plant lines was statistically significant at p ≤ 0.05. Details of the statistical analysis are presented in Additional file 2: Table S3« less

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Works referenced in this record:

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    Figures/Tables have been extracted from DOE-funded journal article accepted manuscripts.