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Title: Engineering electron metabolism to increase ethanol production in Clostridium thermocellum

Here, the NfnAB (NADH-dependent reduced ferredoxin:NADP + oxidoreductase) and Rnf ( Rhodobacter nitrogen fixation) complexes are thought to catalyze electron transfer between reduced ferredoxin and NAD(P) +. Efficient electron flux is critical for engineering fuel production pathways, but little is known about the relative importance of these enzymes in vivo. In this study we investigate the importance of the NfnAB and Rnf complexes in Clostridium thermocellum for growth on cellobiose and Avicel using gene deletion, enzyme assays, and fermentation product analysis. The NfnAB complex does not seem to play a major role in metabolism, since deletion of nfnAB genes had little effect on the distribution of fermentation products. By contrast, the Rnf complex appears to play an important role in ethanol formation. Deletion of rnf genes resulted in a decrease in ethanol formation. Overexpression of rnf genes resulted in an increase in ethanol production of about 30%, but only in strains where the hydG hydrogenase maturation gene was also deleted.
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  1. Dartmouth College, Hanover, NH (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
Grant/Contract Number:
AC05-00OR22725; 4000115284
Accepted Manuscript
Journal Name:
Metabolic Engineering
Additional Journal Information:
Journal Name: Metabolic Engineering; Journal ID: ISSN 1096-7176
Research Org:
Dartmouth College, Hanover, NH (United States); Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
09 BIOMASS FUELS; Clostridium thermocellum; ethanol; rnf; nfnAB; ferredoxin; electron metabolism
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1394381; OSTI ID: 1414311