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Title: Ferredoxin:NAD + oxidoreductase of Thermoanaerobacterium saccharolyticum and its role in ethanol formation [Identification of a ferredoxin:NAD + oxidoreductase of Thermoanaerobacterium saccharolyticum and its role in ethanol formation]

Abstract

Ferredoxin:NAD + oxidoreductase (NADH-FNOR) catalyzes the transfer of electrons from reduced ferredoxin to NAD +. This enzyme has been hypothesized to be the main enzyme responsible for ferredoxin oxidization in the NADH-based ethanol pathway in Thermoanaerobacterium saccharolyticum; however, the corresponding gene has not yet been identified. Here, we identified the Tsac_1705 protein as a candidate FNOR based on the homology of its functional domains. We then confirmed its activity in vitro with a ferredoxin-based FNOR assay. To determine its role in metabolism, the tsac_1705 gene was deleted in different strains of T. saccharolyticum. In wild-type T. saccharolyticum, deletion of tsac_1705 resulted in a 75% loss of NADH-FNOR activity, which indicated that Tsac_1705 is the main NADH-FNOR in T. saccharolyticum. When both NADH- and NADPH-linked FNOR genes were deleted, the ethanol titer decreased and the ratio of ethanol to acetate approached unity, indicative of the absence of FNOR activity. As a result, we tested the effect of heterologous expression of Tsac_1705 in Clostridium thermocellum and found improvements in both the titer and the yield of ethanol.

Authors:
 [1];  [2];  [1];  [1];  [1];  [1]
  1. Dartmouth College, Hanover, NH (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. National Renewable Energy Lab. (NREL), Golden, CO (United States)
Publication Date:
Research Org.:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Org.:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
OSTI Identifier:
1339505
Report Number(s):
NREL/JA-2700-67275
Journal ID: ISSN 0099-2240
Grant/Contract Number:
AC36-08GO28308
Resource Type:
Journal Article: Accepted Manuscript
Journal Name:
Applied and Environmental Microbiology
Additional Journal Information:
Journal Volume: 82; Journal Issue: 24; Journal ID: ISSN 0099-2240
Publisher:
American Society for Microbiology
Country of Publication:
United States
Language:
English
Subject:
09 BIOMASS FUELS; 59 BASIC BIOLOGICAL SCIENCES; metabolic engineering; ferredoxins; ethanol production

Citation Formats

Tian, Liang, Lo, Jonathan, Shao, Xiongjun, Zheng, Tianyong, Olson, Daniel G., and Lynd, Lee R. Ferredoxin:NAD+ oxidoreductase of Thermoanaerobacterium saccharolyticum and its role in ethanol formation [Identification of a ferredoxin:NAD+ oxidoreductase of Thermoanaerobacterium saccharolyticum and its role in ethanol formation]. United States: N. p., 2016. Web. doi:10.1128/AEM.02130-16.
Tian, Liang, Lo, Jonathan, Shao, Xiongjun, Zheng, Tianyong, Olson, Daniel G., & Lynd, Lee R. Ferredoxin:NAD+ oxidoreductase of Thermoanaerobacterium saccharolyticum and its role in ethanol formation [Identification of a ferredoxin:NAD+ oxidoreductase of Thermoanaerobacterium saccharolyticum and its role in ethanol formation]. United States. doi:10.1128/AEM.02130-16.
Tian, Liang, Lo, Jonathan, Shao, Xiongjun, Zheng, Tianyong, Olson, Daniel G., and Lynd, Lee R. Fri . "Ferredoxin:NAD+ oxidoreductase of Thermoanaerobacterium saccharolyticum and its role in ethanol formation [Identification of a ferredoxin:NAD+ oxidoreductase of Thermoanaerobacterium saccharolyticum and its role in ethanol formation]". United States. doi:10.1128/AEM.02130-16. https://www.osti.gov/servlets/purl/1339505.
@article{osti_1339505,
title = {Ferredoxin:NAD+ oxidoreductase of Thermoanaerobacterium saccharolyticum and its role in ethanol formation [Identification of a ferredoxin:NAD+ oxidoreductase of Thermoanaerobacterium saccharolyticum and its role in ethanol formation]},
author = {Tian, Liang and Lo, Jonathan and Shao, Xiongjun and Zheng, Tianyong and Olson, Daniel G. and Lynd, Lee R.},
abstractNote = {Ferredoxin:NAD+ oxidoreductase (NADH-FNOR) catalyzes the transfer of electrons from reduced ferredoxin to NAD+. This enzyme has been hypothesized to be the main enzyme responsible for ferredoxin oxidization in the NADH-based ethanol pathway in Thermoanaerobacterium saccharolyticum; however, the corresponding gene has not yet been identified. Here, we identified the Tsac_1705 protein as a candidate FNOR based on the homology of its functional domains. We then confirmed its activity in vitro with a ferredoxin-based FNOR assay. To determine its role in metabolism, the tsac_1705 gene was deleted in different strains of T. saccharolyticum. In wild-type T. saccharolyticum, deletion of tsac_1705 resulted in a 75% loss of NADH-FNOR activity, which indicated that Tsac_1705 is the main NADH-FNOR in T. saccharolyticum. When both NADH- and NADPH-linked FNOR genes were deleted, the ethanol titer decreased and the ratio of ethanol to acetate approached unity, indicative of the absence of FNOR activity. As a result, we tested the effect of heterologous expression of Tsac_1705 in Clostridium thermocellum and found improvements in both the titer and the yield of ethanol.},
doi = {10.1128/AEM.02130-16},
journal = {Applied and Environmental Microbiology},
number = 24,
volume = 82,
place = {United States},
year = {Fri Sep 30 00:00:00 EDT 2016},
month = {Fri Sep 30 00:00:00 EDT 2016}
}

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