title: Biofuels. Engineering alcohol tolerance in yeast.
abstract: Ethanol toxicity in the yeast Saccharomyces cerevisiae limits titer and productivity in the industrial production of transportation bioethanol. We show that strengthening the opposing potassium and proton electrochemical membrane gradients is a mechanism that enhances general resistance to multiple alcohols. The elevation of extracellular potassium and pH physically bolsters these gradients, increasing tolerance to higher alcohols and ethanol fermentation in commercial and laboratory strains (including a xylose-fermenting strain) under industrial-like conditions. Production per cell remains largely unchanged, with improvements deriving from heightened population viability. Likewise, up-regulation of the potassium and proton pumps in the laboratory strain enhances performance to levels exceeding those of industrial strains. Although genetically complex, alcohol tolerance can thus be dominated by a single cellular process, one controlled by a major physicochemical component but amenable to biological augmentation.
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA. Whitehead Institute for Biomedical Research, Cambridge, MA, USA.
authors.forename: Felix H
authors.initials: FH
authors.lastname: Lam
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA.
authors.forename: Adel
authors.initials: A
authors.lastname: Ghaderi
authors.affiliation: Whitehead Institute for Biomedical Research, Cambridge, MA, USA. gfink@wi.mit.edu gregstep@mit.edu.
authors.forename: Gerald R
authors.initials: GR
authors.lastname: Fink
authors.affiliation: Department of Chemical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA, USA. gfink@wi.mit.edu gregstep@mit.edu.
authors.forename: Gregory
authors.initials: G
authors.lastname: Stephanopoulos
mesh_terms: D056804:Biofuels; D027682:Cation Transport Proteins / Q000235:genetics; D018929:Cell Culture Techniques; D002462:Cell Membrane / Q000378:metabolism; D002616:Chemical Engineering; D025141:Drug Resistance, Fungal / Q000235:genetics; D000431:Ethanol / Q000378:metabolism* / Q000494:pharmacology; D005285:Fermentation; D005818:Genetic Engineering; D005947:Glucose / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D010710:Phosphates / Q000378:metabolism*; D017680:Potassium Compounds / Q000378:metabolism*; D017494:Proton Pumps / Q000235:genetics; D006180:Proton-Translocating ATPases / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000187:drug effects / Q000235:genetics / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics; D015854:Up-Regulation; D014994:Xylose / Q000378:metabolism
chemical_list: D056804:Biofuels; D027682:Cation Transport Proteins; D010710:Phosphates; D017680:Potassium Compounds; D017494:Proton Pumps; D029701:Saccharomyces cerevisiae Proteins; C068664:TRK1 protein, S cerevisiae; D000431:Ethanol; D014994:Xylose; C013216:potassium phosphate; C092477:PMA1 protein, S cerevisiae; D006180:Proton-Translocating ATPases; D005947:Glucose