Membrane Stresses Induced by Overproduction of Free Fatty Acids in Escherichia coli.

Journal Article · Tue Nov 01 00:00:00 EDT 2011 · Applied and Environmental Microbiology

DOI:https://doi.org/10.1128/AEM.05421-11· OSTI ID:1050810

Lennen, Rebecca M; Kruziki, Max A; Kumar, Kritika; Zinkel, Robert A; Burnum, Kristin E; Lipton, Mary S; Hoover, Spencer W; Ranatunga, Don Ruwan; Wittkopp, Tyler M; Marner, II, Wesley D; Pfleger, Brian F

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 conversions 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 titers was observed after 24 h cultivation. The results of this study serve as a baseline for future targeted attempts to improve FFA yields and titers in E. coli.

• Research Organization: Pacific Northwest National Lab. (PNNL), Richland, WA (United States). Environmental Molecular Sciences Lab. (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1050810
• Report Number(s): PNNL-SA-83349; AEMIDF; 29591; KP1601050; TRN: US201218%%1578
• Journal Information: Applied and Environmental Microbiology, Vol. 77, Issue 22; ISSN 0099-2240
• Country of Publication: United States
• Language: English

Related Subjects

59 BASIC BIOLOGICAL SCIENCES
54 ENVIRONMENTAL SCIENCES
ALKANES
BACTERIOPHAGES
BIOFUELS
BIOSYNTHESIS
CARBON SOURCES
CARBOXYLIC ACIDS
CARRIERS
CONTROL
CONVERSION
CULTIVATION
ENERGY DENSITY
ENGINEERING
ESCHERICHIA COLI
ESTERS
GENES
LENGTH
LEVELS
MEMBRANES
MORPHOLOGY
POTENTIALS
PROTEINS
REDUCTION
RESPIRATION
STRAINS
STRESSES
VIABILITY
Environmental Molecular Sciences Laboratory