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Title: The redox-sensing protein Rex modulates ethanol production in Thermoanaerobacterium saccharolyticum

Abstract

Thermoanaerobacterium saccharolyticum is a thermophilic anaerobe that has been engineered to produce high amounts of ethanol, reaching ~90% theoretical yield at a titer of 70 g/L. Here we report the physiological changes that occur upon deleting the redox-sensing transcriptional regulator Rex in wild type T. saccharolyticum: a single deletion of rex resulted in a two-fold increase in ethanol yield (from 40% to 91% theoretical yield), but the resulting strains grew only about a third as fast as the wild type strain. Deletion of the rex gene also had the effect of increasing expression of alcohol dehydrogenase genes, adhE and adhA. After several serial transfers, the ethanol yield decreased from an average of 91% to 55%, and the growth rates had increased. We performed whole-genome resequencing to identify secondary mutations in the Δrex strains adapted for faster growth. In several cases, secondary mutations had appeared in the adhE gene. Furthermore, in these strains the NADH-linked alcohol dehydrogenase activity was greatly reduced. Complementation studies were done to reintroduce rex into the Δ strains: reintroducing rex decreased ethanol yield to below wild type levels in the Δrex strain without adhE mutations, but did not change the ethanol yield in the Δrex strain wheremore » an adhE mutation occurred.« less

Authors:
ORCiD logo; ; ; ORCiD logo;
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)
OSTI Identifier:
1432066
Alternate Identifier(s):
OSTI ID: 1627859
Grant/Contract Number:  
AC05-00OR22725
Resource Type:
Published Article
Journal Name:
PLoS ONE
Additional Journal Information:
Journal Name: PLoS ONE Journal Volume: 13 Journal Issue: 4; Journal ID: ISSN 1932-6203
Publisher:
Public Library of Science
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; Science & Technology - Other Topics

Citation Formats

Zheng, Tianyong, Lanahan, Anthony A., Lynd, Lee R., Olson, Daniel G., and Blanchard, ed., Jeffrey L. The redox-sensing protein Rex modulates ethanol production in Thermoanaerobacterium saccharolyticum. United States: N. p., 2018. Web. doi:10.1371/journal.pone.0195143.
Zheng, Tianyong, Lanahan, Anthony A., Lynd, Lee R., Olson, Daniel G., & Blanchard, ed., Jeffrey L. The redox-sensing protein Rex modulates ethanol production in Thermoanaerobacterium saccharolyticum. United States. doi:https://doi.org/10.1371/journal.pone.0195143
Zheng, Tianyong, Lanahan, Anthony A., Lynd, Lee R., Olson, Daniel G., and Blanchard, ed., Jeffrey L. Thu . "The redox-sensing protein Rex modulates ethanol production in Thermoanaerobacterium saccharolyticum". United States. doi:https://doi.org/10.1371/journal.pone.0195143.
@article{osti_1432066,
title = {The redox-sensing protein Rex modulates ethanol production in Thermoanaerobacterium saccharolyticum},
author = {Zheng, Tianyong and Lanahan, Anthony A. and Lynd, Lee R. and Olson, Daniel G. and Blanchard, ed., Jeffrey L.},
abstractNote = {Thermoanaerobacterium saccharolyticum is a thermophilic anaerobe that has been engineered to produce high amounts of ethanol, reaching ~90% theoretical yield at a titer of 70 g/L. Here we report the physiological changes that occur upon deleting the redox-sensing transcriptional regulator Rex in wild type T. saccharolyticum: a single deletion of rex resulted in a two-fold increase in ethanol yield (from 40% to 91% theoretical yield), but the resulting strains grew only about a third as fast as the wild type strain. Deletion of the rex gene also had the effect of increasing expression of alcohol dehydrogenase genes, adhE and adhA. After several serial transfers, the ethanol yield decreased from an average of 91% to 55%, and the growth rates had increased. We performed whole-genome resequencing to identify secondary mutations in the Δrex strains adapted for faster growth. In several cases, secondary mutations had appeared in the adhE gene. Furthermore, in these strains the NADH-linked alcohol dehydrogenase activity was greatly reduced. Complementation studies were done to reintroduce rex into the Δ strains: reintroducing rex decreased ethanol yield to below wild type levels in the Δrex strain without adhE mutations, but did not change the ethanol yield in the Δrex strain where an adhE mutation occurred.},
doi = {10.1371/journal.pone.0195143},
journal = {PLoS ONE},
number = 4,
volume = 13,
place = {United States},
year = {2018},
month = {4}
}

Journal Article:
Free Publicly Available Full Text
Publisher's Version of Record
DOI: https://doi.org/10.1371/journal.pone.0195143

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