title: Sphingolipids contribute to acetic acid resistance in Zygosaccharomyces bailii.
abstract: Lignocellulosic raw material plays a crucial role in the development of sustainable processes for the production of fuels and chemicals. Weak acids such as acetic acid and formic acid are troublesome inhibitors restricting efficient microbial conversion of the biomass to desired products. To improve our understanding of weak acid inhibition and to identify engineering strategies to reduce acetic acid toxicity, the highly acetic-acid-tolerant yeast Zygosaccharomyces bailii was studied. The impact of acetic acid membrane permeability on acetic acid tolerance in Z. bailii was investigated with particular focus on how the previously demonstrated high sphingolipid content in the plasma membrane influences acetic acid tolerance and membrane permeability. Through molecular dynamics simulations, we concluded that membranes with a high content of sphingolipids are thicker and more dense, increasing the free energy barrier for the permeation of acetic acid through the membrane. Z. bailii cultured with the drug myriocin, known to decrease cellular sphingo-lipid levels, exhibited significant growth inhibition in the presence of acetic acid, while growth in medium without acetic acid was unaffected by the myriocin addition. Furthermore, following an acetic acid pulse, the intracellular pH decreased more in myriocin-treated cells than in control cells. This indicates a higher inflow rate of acetic acid and confirms that the reduction in growth of cells cultured with myriocin in the medium with acetic acid was due to an increase in membrane permeability, thereby demonstrating the importance of a high fraction of sphingolipids in the membrane of Z. bailii to facilitate acetic acid resistance; a property potentially transferable to desired production organisms suffering from weak acid stress.
authors.affiliation: Department of Biology and Biological Engineering, Division of Industrial Biotechnology, Chalmers University of Technology, Gothenburg, Sweden.
authors.forename: Lina
authors.initials: L
authors.lastname: Lindahl
authors.affiliation: School of Chemistry, University of Southampton, Highfield, Southampton, United Kingdom.|Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Samuel
authors.initials: S
authors.lastname: Genheden
authors.affiliation: Department of Chemistry and Molecular Biology, University of Gothenburg, Gothenburg, Sweden.
authors.forename: Leif A
authors.initials: LA
authors.lastname: Eriksson
authors.affiliation: Department of Biology and Biological Engineering, Division of Industrial Biotechnology, Chalmers University of Technology, Gothenburg, Sweden.
authors.forename: Lisbeth
authors.initials: L
authors.lastname: Olsson
authors.affiliation: Department of Biology and Biological Engineering, Division of Industrial Biotechnology, Chalmers University of Technology, Gothenburg, Sweden. maurizio.bettiga@chalmers.se.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Bettiga
mesh_terms: D019342:Acetic Acid / Q000633:toxicity*; D000935:Antifungal Agents / Q000378:metabolism; D002462:Cell Membrane / Q000187:drug effects; D003470:Culture Media / Q000737:chemistry; D005229:Fatty Acids, Monounsaturated / Q000378:metabolism; D008031:Lignin / Q000378:metabolism*; D056004:Molecular Dynamics Simulation; D010539:Permeability / Q000187:drug effects; D013107:Sphingolipids / Q000378:metabolism*; D020068:Zygosaccharomyces / Q000187:drug effects* / Q000254:growth & development / Q000378:metabolism*
chemical_list: D000935:Antifungal Agents; D003470:Culture Media; D005229:Fatty Acids, Monounsaturated; D013107:Sphingolipids; C036909:lignocellulose; D008031:Lignin; D019342:Acetic Acid; C001996:thermozymocidin
keywords: acetic acid tolerance; inhibitors; lignocellulose; membrane permeability; molecular dynamics simulations; myriocin