title: An auto-inducible mechanism for ionic liquid resistance in microbial biofuel production.
abstract: Ionic liquids (ILs) are emerging as superior solvents for numerous industrial applications, including the pretreatment of biomass for the microbial production of biofuels. However, some of the most effective ILs used to solubilize cellulose inhibit microbial growth, decreasing efficiency in the overall process. Here we identify an IL-resistance mechanism consisting of two adjacent genes from Enterobacter lignolyticus, a rain forest soil bacterium that is tolerant to an imidazolium-based IL. These genes retain their full functionality when transferred to an Escherichia coli biofuel host, with IL resistance established by an inner membrane transporter, regulated by an IL-inducible repressor. Expression of the transporter is dynamically adjusted in direct response to IL, enabling growth and biofuel production at levels of IL that are toxic to native strains. This natural auto-regulatory system provides the basis for engineering IL-tolerant microbes, which should accelerate progress towards effective conversion of lignocellulosic biomass to fuels and renewable chemicals.
authors.affiliation: 1] Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, California 94608, USA [2] Institute of Botany, University of Basel, Basel 4056, Switzerland [3] Biology and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
authors.forename: Thomas L
authors.initials: TL
authors.lastname: Ruegg
authors.affiliation: 1] Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, California 94608, USA [2] Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Eun-Mi
authors.initials: EM
authors.lastname: Kim
authors.affiliation: 1] Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, California 94608, USA [2] Biological and Materials Science Center, Sandia National Laboratories, Livermore, California 94550, USA.
authors.forename: Blake A
authors.initials: BA
authors.lastname: Simmons
authors.affiliation: 1] Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, California 94608, USA [2] Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA [3] Department of Chemical and Biomolecular Engineering, Department of Bioengineering, University of California, Berkeley, California 94720, USA.
authors.forename: Jay D
authors.initials: JD
authors.lastname: Keasling
authors.affiliation: 1] Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, California 94608, USA [2] Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Steven W
authors.initials: SW
authors.lastname: Singer
authors.affiliation: 1] Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, California 94608, USA [2] Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA.
authors.forename: Taek Soon
authors.initials: TS
authors.lastname: Lee
authors.affiliation: 1] Joint BioEnergy Institute, 5885 Hollis Street, Emeryville, California 94608, USA [2] Biology and Biotechnology Division, Lawrence Livermore National Laboratory, Livermore, California 94550, USA.
authors.forename: Michael P
authors.initials: MP
authors.lastname: Thelen
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics*; D056804:Biofuels; D018533:Biomass; D024881:Drug Resistance, Bacterial / Q000235:genetics*; D004754:Enterobacter / Q000187:drug effects / Q000235:genetics* / Q000502:physiology; D004926:Escherichia coli; D007093:Imidazoles / Q000494:pharmacology*; D052578:Ionic Liquids / Q000494:pharmacology*; D012997:Solvents
chemical_list: D001426:Bacterial Proteins; D056804:Biofuels; D007093:Imidazoles; D052578:Ionic Liquids; D012997:Solvents