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Title: Lignocellulose fermentation and residual solids characterization for senescent switchgrass fermentation by Clostridium thermocellum in the presence and absence of continuous in situ ball-milling

Abstract

Milling during lignocellulosic fermentation, henceforth referred to as cotreatment, is investigated as an alternative to thermochemical pretreatment as a means of enhancing biological solubilization of lignocellulose. We investigate the impact of milling on soluble substrate fermentation by Clostridium thermocellum with comparison to yeast, document solubilization for fermentation of senescent switchgrass with and without ball milling, and characterize residual solids. Soluble substrate fermentation by C. thermocellum proceeded readily in the presence of continuous ball milling but was completely arrested for yeast. Total fractional carbohydrate solubilization achieved after fermentation of senescent switchgrass by C. thermocellum for 5 days was 0.45 without cotreatment or pretreatment, 0.81 with hydrothermal pretreatment (200 degrees C, 15 minutes, severity 4.2), and 0.88 with cotreatment. Acetate and ethanol were the main fermentation products, and were produced at similar ratios with and without cotreatment. Analysis of solid residues was undertaken using molecular beam mass spectrometry (PyMBMS) and solid-state nuclear magnetic resonance spectroscopy (NMR) in order to provide insight into changes in plant cell walls during processing via various modes. The structure of lignin present in residual solids remaining after fermentation with cotreatment appeared to change little, with substantially greater changes observed for hydrothermal pretreatment - particularly with respect tomore » formation of C-C bonds. The observation of high solubilization with little apparent modification of the residue is consistent with cotreatment enhancing solubilization primarily by increasing the access of saccharolytic enzymes to the feedstock, and C. thermocellum being able to attack all the major linkages in cellulosic biomass provided that these linkages are accessible.« less

Authors:
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Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Office of Biological and Environmental Research
OSTI Identifier:
1364048
Report Number(s):
NREL/JA-2700-68688
Journal ID: ISSN 1754-5692; EESNBY
DOE Contract Number:  
AC36-08GO28308
Resource Type:
Journal Article
Journal Name:
Energy & Environmental Science
Additional Journal Information:
Journal Volume: 10; Journal Issue: 5; Journal ID: ISSN 1754-5692
Publisher:
Royal Society of Chemistry
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; lignocellulosic fermentation; treatment

Citation Formats

Balch, Michael L., Holwerda, Evert K., Davis, Mark F., Sykes, Robert W., Happs, Renee M., Kumar, Rajeev, Wyman, Charles E., and Lynd, Lee R. Lignocellulose fermentation and residual solids characterization for senescent switchgrass fermentation by Clostridium thermocellum in the presence and absence of continuous in situ ball-milling. United States: N. p., 2017. Web. doi:10.1039/C6EE03748H.
Balch, Michael L., Holwerda, Evert K., Davis, Mark F., Sykes, Robert W., Happs, Renee M., Kumar, Rajeev, Wyman, Charles E., & Lynd, Lee R. Lignocellulose fermentation and residual solids characterization for senescent switchgrass fermentation by Clostridium thermocellum in the presence and absence of continuous in situ ball-milling. United States. doi:10.1039/C6EE03748H.
Balch, Michael L., Holwerda, Evert K., Davis, Mark F., Sykes, Robert W., Happs, Renee M., Kumar, Rajeev, Wyman, Charles E., and Lynd, Lee R. Wed . "Lignocellulose fermentation and residual solids characterization for senescent switchgrass fermentation by Clostridium thermocellum in the presence and absence of continuous in situ ball-milling". United States. doi:10.1039/C6EE03748H.
@article{osti_1364048,
title = {Lignocellulose fermentation and residual solids characterization for senescent switchgrass fermentation by Clostridium thermocellum in the presence and absence of continuous in situ ball-milling},
author = {Balch, Michael L. and Holwerda, Evert K. and Davis, Mark F. and Sykes, Robert W. and Happs, Renee M. and Kumar, Rajeev and Wyman, Charles E. and Lynd, Lee R.},
abstractNote = {Milling during lignocellulosic fermentation, henceforth referred to as cotreatment, is investigated as an alternative to thermochemical pretreatment as a means of enhancing biological solubilization of lignocellulose. We investigate the impact of milling on soluble substrate fermentation by Clostridium thermocellum with comparison to yeast, document solubilization for fermentation of senescent switchgrass with and without ball milling, and characterize residual solids. Soluble substrate fermentation by C. thermocellum proceeded readily in the presence of continuous ball milling but was completely arrested for yeast. Total fractional carbohydrate solubilization achieved after fermentation of senescent switchgrass by C. thermocellum for 5 days was 0.45 without cotreatment or pretreatment, 0.81 with hydrothermal pretreatment (200 degrees C, 15 minutes, severity 4.2), and 0.88 with cotreatment. Acetate and ethanol were the main fermentation products, and were produced at similar ratios with and without cotreatment. Analysis of solid residues was undertaken using molecular beam mass spectrometry (PyMBMS) and solid-state nuclear magnetic resonance spectroscopy (NMR) in order to provide insight into changes in plant cell walls during processing via various modes. The structure of lignin present in residual solids remaining after fermentation with cotreatment appeared to change little, with substantially greater changes observed for hydrothermal pretreatment - particularly with respect to formation of C-C bonds. The observation of high solubilization with little apparent modification of the residue is consistent with cotreatment enhancing solubilization primarily by increasing the access of saccharolytic enzymes to the feedstock, and C. thermocellum being able to attack all the major linkages in cellulosic biomass provided that these linkages are accessible.},
doi = {10.1039/C6EE03748H},
journal = {Energy & Environmental Science},
issn = {1754-5692},
number = 5,
volume = 10,
place = {United States},
year = {2017},
month = {4}
}