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Title: Simultaneous achievement of high ethanol yield and titer in Clostridium thermocellum

Abstract

Background Biofuel production from plant cell walls offers the potential for sustainable and economically attractive alternatives to petroleum-based products. Fuels from cellulosic biomass are particularly promising, but would benefit from lower processing costs. Clostridium thermocellum can rapidly solubilize and ferment cellulosic biomass, making it a promising candidate microorganism for consolidated bioprocessing for biofuel production, but increases in product yield and titer are still needed. Results We started with an engineered C. thermocellum strain where the central metabolic pathways to products other than ethanol had been deleted. After two stages of adaptive evolution, an evolved strain was selected with improved yield and titer. On chemically defined medium with crystalline cellulose as substrate, the evolved strain produced 22.4 ± 1.4 g/L ethanol from 60 g/L cellulose. Moreover, the resulting yield was about 0.39 gETOH/gGluc eq, which is 75 % of the maximum theoretical yield. Genome resequencing, proteomics, and biochemical analysis were used to examine differences between the original and evolved strains. Conclusions A two step selection method successfully improved the ethanol yield and the titer. Finaly, this evolved strain has the highest ethanol yield and titer reported to date for C. thermocellum, and is an important step in the development of thismore » microbe for industrial applications.« less

Authors:
 [1];  [2];  [1];  [3];  [1];  [1];  [1];  [1];  [2];  [3];  [3];  [2];  [1]
  1. Dartmouth College, Hanover, NH (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Univ. of Tennessee, Knoxville, TN (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  3. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Research Org.:
Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). BioEnergy Science Center (BESC)
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:
1286977
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Accepted Manuscript
Journal Name:
Biotechnology for Biofuels
Additional Journal Information:
Journal Volume: 9; Journal Issue: 1; Journal ID: ISSN 1754-6834
Publisher:
BioMed Central
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; 59 BASIC BIOLOGICAL SCIENCES; consolidated bioprocessing; clostridium thermocellum; cellulosic ethanol; adapative evolution

Citation Formats

Tian, Liang, Papanek, Beth, Olson, Daniel G., Rydzak, Thomas, Holwerda, Evert K., Zheng, Tianyong, Zhou, Jilai, Maloney, Marybeth, Jiang, Nannan, Giannone, Richard J., Hettich, Robert L., Guss, Adam M., and Lynd, Lee R.. Simultaneous achievement of high ethanol yield and titer in Clostridium thermocellum. United States: N. p., 2016. Web. doi:10.1186/s13068-016-0528-8.
Tian, Liang, Papanek, Beth, Olson, Daniel G., Rydzak, Thomas, Holwerda, Evert K., Zheng, Tianyong, Zhou, Jilai, Maloney, Marybeth, Jiang, Nannan, Giannone, Richard J., Hettich, Robert L., Guss, Adam M., & Lynd, Lee R.. Simultaneous achievement of high ethanol yield and titer in Clostridium thermocellum. United States. doi:10.1186/s13068-016-0528-8.
Tian, Liang, Papanek, Beth, Olson, Daniel G., Rydzak, Thomas, Holwerda, Evert K., Zheng, Tianyong, Zhou, Jilai, Maloney, Marybeth, Jiang, Nannan, Giannone, Richard J., Hettich, Robert L., Guss, Adam M., and Lynd, Lee R.. Thu . "Simultaneous achievement of high ethanol yield and titer in Clostridium thermocellum". United States. doi:10.1186/s13068-016-0528-8. https://www.osti.gov/servlets/purl/1286977.
@article{osti_1286977,
title = {Simultaneous achievement of high ethanol yield and titer in Clostridium thermocellum},
author = {Tian, Liang and Papanek, Beth and Olson, Daniel G. and Rydzak, Thomas and Holwerda, Evert K. and Zheng, Tianyong and Zhou, Jilai and Maloney, Marybeth and Jiang, Nannan and Giannone, Richard J. and Hettich, Robert L. and Guss, Adam M. and Lynd, Lee R.},
abstractNote = {Background Biofuel production from plant cell walls offers the potential for sustainable and economically attractive alternatives to petroleum-based products. Fuels from cellulosic biomass are particularly promising, but would benefit from lower processing costs. Clostridium thermocellum can rapidly solubilize and ferment cellulosic biomass, making it a promising candidate microorganism for consolidated bioprocessing for biofuel production, but increases in product yield and titer are still needed. Results We started with an engineered C. thermocellum strain where the central metabolic pathways to products other than ethanol had been deleted. After two stages of adaptive evolution, an evolved strain was selected with improved yield and titer. On chemically defined medium with crystalline cellulose as substrate, the evolved strain produced 22.4 ± 1.4 g/L ethanol from 60 g/L cellulose. Moreover, the resulting yield was about 0.39 gETOH/gGluc eq, which is 75 % of the maximum theoretical yield. Genome resequencing, proteomics, and biochemical analysis were used to examine differences between the original and evolved strains. Conclusions A two step selection method successfully improved the ethanol yield and the titer. Finaly, this evolved strain has the highest ethanol yield and titer reported to date for C. thermocellum, and is an important step in the development of this microbe for industrial applications.},
doi = {10.1186/s13068-016-0528-8},
journal = {Biotechnology for Biofuels},
number = 1,
volume = 9,
place = {United States},
year = {2016},
month = {6}
}

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