Document Detail

Membrane stresses induced by overproduction of free fatty acids in Escherichia coli.
MedLine Citation:
PMID:  21948837     Owner:  NLM     Status:  MEDLINE    
Microbially produced fatty acids are potential precursors to high-energy-density biofuels, including alkanes and alkyl ethyl esters, by either catalytic conversion of free fatty acids (FFAs) or enzymatic conversion of acyl-acyl carrier protein or acyl-coenzyme A intermediates. Metabolic engineering efforts aimed at overproducing FFAs in Escherichia coli have achieved less than 30% of the maximum theoretical yield on the supplied carbon source. In this work, the viability, morphology, transcript levels, and protein levels of a strain of E. coli that overproduces medium-chain-length FFAs was compared to an engineered control strain. By early stationary phase, an 85% reduction in viable cell counts and exacerbated loss of inner membrane integrity were observed in the FFA-overproducing strain. These effects were enhanced in strains endogenously producing FFAs compared to strains exposed to exogenously fed FFAs. Under two sets of cultivation conditions, long-chain unsaturated fatty acid content greatly increased, and the expression of genes and proteins required for unsaturated fatty acid biosynthesis were significantly decreased. Membrane stresses were further implicated by increased expression of genes and proteins of the phage shock response, the MarA/Rob/SoxS regulon, and the nuo and cyo operons of aerobic respiration. Gene deletion studies confirmed the importance of the phage shock proteins and Rob for maintaining cell viability; however, little to no change in FFA titer was observed after 24 h of cultivation. The results of this study serve as a baseline for future targeted attempts to improve FFA yields and titers in E. coli.
Rebecca M Lennen; Max A Kruziki; Kritika Kumar; Robert A Zinkel; Kristin E Burnum; Mary S Lipton; Spencer W Hoover; Don R Ranatunga; Tyler M Wittkopp; Wesley D Marner; Brian F Pfleger
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Publication Detail:
Type:  Journal Article; Research Support, N.I.H., Extramural; Research Support, Non-U.S. Gov't; Research Support, U.S. Gov't, Non-P.H.S.     Date:  2011-09-23
Journal Detail:
Title:  Applied and environmental microbiology     Volume:  77     ISSN:  1098-5336     ISO Abbreviation:  Appl. Environ. Microbiol.     Publication Date:  2011 Nov 
Date Detail:
Created Date:  2011-11-03     Completed Date:  2012-02-21     Revised Date:  2013-06-27    
Medline Journal Info:
Nlm Unique ID:  7605801     Medline TA:  Appl Environ Microbiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  8114-28     Citation Subset:  IM    
Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Drive, Madison, WI 53706, USA.
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MeSH Terms
Cell Membrane / drug effects,  metabolism,  physiology*
Escherichia coli / cytology,  genetics,  metabolism,  physiology*
Escherichia coli Proteins / analysis
Fatty Acids, Nonesterified / biosynthesis*
Gene Expression Profiling
Microbial Viability / drug effects
Organisms, Genetically Modified / genetics,  metabolism,  physiology
Stress, Physiological*
Reg. No./Substance:
0/Escherichia coli Proteins; 0/Fatty Acids, Nonesterified

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