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Title: Study of traits and recalcitrance reduction of field-grown COMT down-regulated switchgrass

Abstract

The native recalcitrance of plants hinders the biomass conversion process using current biorefinery techniques. Down-regulation of the caffeic acid O-methyltransferase (COMT) gene in the lignin biosynthesis pathway of switchgrass reduced the thermochemical and biochemical conversion recalcitrance of biomass. Due to potential environmental influences on lignin biosynthesis and deposition, studying the consequences of physicochemical changes in field-grown plants without pretreatment is essential to evaluate the performance of lignin-altered plants. In this study, we determined the chemical composition, cellulose crystallinity and the degree of its polymerization, molecular weight of hemicellulose, and cellulose accessibility of cell walls in order to better understand the fundamental features of why biomass is recalcitrant to conversion without pretreatment. The most important is to investigate whether traits and features are stable in the dynamics of field environmental effects over multiple years.

Authors:
 [1];  [1];  [1];  [2];  [2];  [2];  [2];  [1];  [1];  [3];  [3];  [4];  [4];  [5];  [6];  [7];  [4];  [8]
  1. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC), BioSciences Division, and UT-ORNL Joint Institute for Biological Sciences
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States). Biosciences Center
  3. National Renewable Energy Lab. (NREL), Golden, CO (United States). National Bioenergy Center
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC); Univ. of Tennessee, Knoxville, TN (United States). Department of Plant Sciences
  5. The Samuel Roberts Noble Foundation, Ardmore, OK (United States). Forage Improvement Division
  6. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC); Univ. of North Texas, Denton, TX (United States). BioDiscovery Institute and Department of Biological Sciences
  7. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC); The Samuel Roberts Noble Foundation, Ardmore, OK (United States). Forage Improvement Division
  8. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC), BioSciences Division, and UT-ORNL Joint Institute for Biological Sciences; Univ. of Tennessee, Knoxville, TN (United States). Department of Chemical and Biomolecular Engineering & Department of Forestry, Wildlife and Fisheries
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC); Joint Institute for Biological Sciences (JIBS); National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
OSTI Identifier:
1339385
Alternate Identifier(s):
OSTI ID: 1340901
Report Number(s):
NREL/JA-5100-67649
Journal ID: ISSN 1754-6834
Grant/Contract Number:
AC05-00OR22725; AC36-08GO28308
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; 37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 59 BASIC BIOLOGICAL SCIENCES; Switchgrass; Caffeic acid O-methyltransferase; Biomass recalcitrance; Enzymatic hydrolysis; Lignin; Cellulose accessibility; switchgrass; caffeic acid; O-methyltransferase; biomass recalcitrance; enzymatic hydrolysis; lignin; cellulose accessibility

Citation Formats

Li, Mi, Pu, Yunqiao, Yoo, Chang Geun, Gjersing, Erica, Decker, Stephen R., Doeppke, Crissa, Shollenberger, Todd, Tschaplinski, Timothy J., Engle, Nancy L., Sykes, Robert W., Davis, Mark F., Baxter, Holly L., Mazarei, Mitra, Fu, Chunxiang, Dixon, Richard A., Wang, Zeng-Yu, Neal Stewart, C., and Ragauskas, Arthur J. Study of traits and recalcitrance reduction of field-grown COMT down-regulated switchgrass. United States: N. p., 2017. Web. doi:10.1186/s13068-016-0695-7.
Li, Mi, Pu, Yunqiao, Yoo, Chang Geun, Gjersing, Erica, Decker, Stephen R., Doeppke, Crissa, Shollenberger, Todd, Tschaplinski, Timothy J., Engle, Nancy L., Sykes, Robert W., Davis, Mark F., Baxter, Holly L., Mazarei, Mitra, Fu, Chunxiang, Dixon, Richard A., Wang, Zeng-Yu, Neal Stewart, C., & Ragauskas, Arthur J. Study of traits and recalcitrance reduction of field-grown COMT down-regulated switchgrass. United States. doi:10.1186/s13068-016-0695-7.
Li, Mi, Pu, Yunqiao, Yoo, Chang Geun, Gjersing, Erica, Decker, Stephen R., Doeppke, Crissa, Shollenberger, Todd, Tschaplinski, Timothy J., Engle, Nancy L., Sykes, Robert W., Davis, Mark F., Baxter, Holly L., Mazarei, Mitra, Fu, Chunxiang, Dixon, Richard A., Wang, Zeng-Yu, Neal Stewart, C., and Ragauskas, Arthur J. Tue . "Study of traits and recalcitrance reduction of field-grown COMT down-regulated switchgrass". United States. doi:10.1186/s13068-016-0695-7. https://www.osti.gov/servlets/purl/1339385.
@article{osti_1339385,
title = {Study of traits and recalcitrance reduction of field-grown COMT down-regulated switchgrass},
author = {Li, Mi and Pu, Yunqiao and Yoo, Chang Geun and Gjersing, Erica and Decker, Stephen R. and Doeppke, Crissa and Shollenberger, Todd and Tschaplinski, Timothy J. and Engle, Nancy L. and Sykes, Robert W. and Davis, Mark F. and Baxter, Holly L. and Mazarei, Mitra and Fu, Chunxiang and Dixon, Richard A. and Wang, Zeng-Yu and Neal Stewart, C. and Ragauskas, Arthur J.},
abstractNote = {The native recalcitrance of plants hinders the biomass conversion process using current biorefinery techniques. Down-regulation of the caffeic acid O-methyltransferase (COMT) gene in the lignin biosynthesis pathway of switchgrass reduced the thermochemical and biochemical conversion recalcitrance of biomass. Due to potential environmental influences on lignin biosynthesis and deposition, studying the consequences of physicochemical changes in field-grown plants without pretreatment is essential to evaluate the performance of lignin-altered plants. In this study, we determined the chemical composition, cellulose crystallinity and the degree of its polymerization, molecular weight of hemicellulose, and cellulose accessibility of cell walls in order to better understand the fundamental features of why biomass is recalcitrant to conversion without pretreatment. The most important is to investigate whether traits and features are stable in the dynamics of field environmental effects over multiple years.},
doi = {10.1186/s13068-016-0695-7},
journal = {Biotechnology for Biofuels},
number = 1,
volume = 10,
place = {United States},
year = {Tue Jan 03 00:00:00 EST 2017},
month = {Tue Jan 03 00:00:00 EST 2017}
}

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  • The native recalcitrance of plants hinders the biomass conversion process using current biorefinery techniques. Down-regulation of the caffeic acid O-methyltransferase ( COMT) gene in the lignin biosynthesis pathway of switchgrass reduced the thermochemical and biochemical conversion recalcitrance of biomass. Due to potential environmental influences on lignin biosynthesis and deposition, studying the consequences of physicochemical changes in field-grown plants without pretreatment is essential to evaluate the performance of lignin-altered plants. We determined the chemical composition, cellulose crystallinity and the degree of its polymerization, molecular weight of hemicellulose, and cellulose accessibility of cell walls in order to better understand the fundamental featuresmore » of why biomass is recalcitrant to conversion without pretreatment. Lastly, the most important is to investigate whether traits and features are stable in the dynamics of field environmental effects over multiple years.« less
  • Transgenic switchgrass (Panicum virgatum L.) has been produced for improved cell walls for biofuels. For instance, downregulated caffeic acid 3-O-methyltransferase (COMT) switchgrass produced significantly more biomass and biofuel than the non-transgenic progenitor line. In this present study we sought to further improve biomass characteristics by crossing the downregulated COMT T 1 lines with high-yielding switchgrass accessions in two genetic backgrounds ('Alamo' and 'Kanlow'). Crosses and T 2 progeny analyses were made under greenhouse conditions to assess maternal effects, plant morphology and yield, and cell wall traits. Female parent type influenced morphology, but had no effect on cell wall traits. Tmore » 2 hybrids produced with T 1 COMT-downregulated switchgrass as the female parent were taller, produced more tillers, and produced 63% more biomass compared with those produced using the field selected accession as the female parent. Transgene status (presence or absence of transgene) influenced both growth and cell wall traits. T 2 transgenic hybrids were 7% shorter 80 days after sowing and produced 43% less biomass than non-transgenic null-segregant hybrids. Cell wall-related differences included lower lignin content, reduced syringyl-to-guaiacyl (S/G) lignin monomer ratio, and a 12% increase in total sugar release in the T 2 transgenic hybrids compared to non-transgenic null segregants. This is the first study to evaluate the feasibility of transferring the low-recalcitrance traits associated with a transgenic switchgrass line into high-yielding field varieties in an attempt to improve growth-related traits. Lastly, our results provide insights into the possible improvement of switchgrass productivity via biotechnology paired with plant breeding.« less
  • Modifying plant cell walls by manipulating lignin biosynthesis can improve biofuel yields from lignocellulosic crops. For example, transgenic switchgrass lines with downregulated expression of caffeic acid O-methyltransferase, a lignin biosynthetic enzyme, produce up to 38% more ethanol than controls. The aim of the present study was to understand cell wall lignification over the second and third growing seasons of COMT-downregulated field-grown switchgrass. COMT gene expression, lignification, and cell wall recalcitrance were assayed for two independent transgenic lines at monthly intervals. Switchgrass rust (Puccinia emaculata) incidence was also tracked across the seasons. Trends in lignification over time differed between the 2more » years. In 2012, sampling was initiated in mid-growing season on reproductive-stage plants and there was little variation in the lignin content of all lines (COMT-downregulated and control) over time. COMT-downregulated lines maintained 11-16% less lignin, 33-40% lower S/G (syringyl-to-guaiacyl) ratios, and 15-42% higher sugar release relative to controls for all time points. In 2013, sampling was initiated earlier in the season on elongation-stage plants and the lignin content of all lines steadily increased over time, while sugar release expectedly decreased. S/G ratios increased in non-transgenic control plants as biomass accumulated over the season, while remaining relatively stable across the season in the COMT-downregulated lines. Differences in cell wall chemistry between transgenic and non-transgenic lines were not apparent until plants transitioned to reproductive growth in mid-season, after which the cell walls of COMT-downregulated plants exhibited phenotypes consistent with what was observed in 2012. There were no differences in rust damage between transgenics and controls at any time point. Finally, these results provide relevant fundamental insights into the process of lignification in a maturing field-grown biofuel feedstock with downregulated lignin biosynthesis.« less
  • Five different types of transgenic ( GAUT4, miRNA, MYB4, COMT and FPGS) Panicum virgatum L. (switchgrass) were grown in a field in Knoxville, Tenn., USA over two consecutive years between 2011 and 2015 in separate experiments. Clonal replicates were established (year-one) and produced much greater biomass during the second year. After each growing season the above ground biomass was analyzed for cell wall sugars and for recalcitrance to enzymatic digestibility, and biofuel using a separate hydrolysis and fermentation (SHF) screen. Here, each transgenic event and control had more glucan, xylan and less ethanol (g/g basis) from the second year ofmore » growth relative to the first year plants. There was no correlation between plant carbohydrate content and biofuel production. In each of cell wall-targeted transgenics, GAUT4, MYB4, COMT and FPGS, the second year of growth resulted in increased carbohydrate abundance (up to 12%) and reduced recalcitrance through higher ethanol yields (up to 21%) over the non-transgenic control plants.« less