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ChemSusChem. 2015 Nov;8(21):3718-26. doi: 10.1002/cssc.201500194. Epub 2015 Sep 25.

Increased Microbial Butanol Tolerance by Exogenous Membrane Insertion Molecules.

Author information

1
Singapore Centre for Environmental Life Sciences Engineering (SCELSE), Nanyang Technological University, Singapore, 637551, Singapore. jhinks@ntu.edu.sg.
2
School of Biological Sciences, Nanyang Technological University, Singapore, 637551, Singapore.
3
Division of Molecular Genetics and Cell Biology, School of Biological Sciences, Nanyang Technological University, Singapore, 637551, Singapore.
4
Singapore Centre for Environmental Life Sciences Engineering (SCELSE), Nanyang Technological University, Singapore, 637551, Singapore.
5
Centre for Marine BioInnovation and School of Biotechnology and Bimolecular Sciences, University of New South Wales, Sydney, 2052, Australia.
6
Department of Chemistry & Biochemistry and Materials, Center for Polymers and Organic Solids, University of California, Santa Barbara, California, 93106, USA.
7
Department of Civil and Environmental Engineering, University of California, Davis, California, 95616, USA.
8
Singapore Centre for Environmental Life Sciences Engineering (SCELSE), Nanyang Technological University, Singapore, 637551, Singapore. twseviour@ntu.edu.sg.

Abstract

Butanol is an ideal biofuel, although poor titers lead to high recovery costs by distillation. Fluidization of microbial membranes by butanol is one of the major factors limiting titers in butanol-producing bioprocesses. Starting with the hypothesis that certain membrane insertion molecules would stabilize the lipid bilayer in the presence of butanol, we applied a combination of in vivo and in vitro techniques within an in silico framework to describe a new approach to achieve solvent tolerance in bacteria. Single-molecule tracking of a model supported bilayer showed that COE1-5C, a five-ringed oligo-polyphenylenevinylene conjugated oligoelectrolyte (COE), reduced the diffusion rate of phospholipids in a microbially derived lipid bilayer to a greater extent than three-ringed and four-ringed COEs. Furthermore, COE1-5C treatment increased the specific growth rate of E. coli K12 relative to a control at inhibitory butanol concentrations. Consequently, to confer butanol tolerance to microbes by exogenous means is complementary to genetic modification of strains in industrial bioprocesses, extends the physiological range of microbes to match favorable bioprocess conditions, and is amenable with complex and undefined microbial consortia for biobutanol production. Molecular dynamics simulations indicated that the π-conjugated aromatic backbone of COE1-5C likely acts as a hydrophobic tether for glycerophospholipid acyl chains by enhancing bilayer integrity in the presence of high butanol concentrations, which thereby counters membrane fluidization. COE1-5C-mitigated E. coli K12 membrane depolarization by butanol is consistent with the hypothesis that improved growth rates in the presence of butanol are a consequence of improved bilayer stability.

KEYWORDS:

biotechnology; membranes; microbial solvent tolerance; microbiology; molecular dynamics

PMID:
26404512
DOI:
10.1002/cssc.201500194
[Indexed for MEDLINE]

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