title: Biofuels. Altered sterol composition renders yeast thermotolerant.
abstract: Ethanol production for use as a biofuel is mainly achieved through simultaneous saccharification and fermentation by yeast. Operating at ≥40°C would be beneficial in terms of increasing efficiency of the process and reducing costs, but yeast does not grow efficiently at those temperatures. We used adaptive laboratory evolution to select yeast strains with improved growth and ethanol production at ≥40°C. Sequencing of the whole genome, genome-wide gene expression, and metabolic-flux analyses revealed a change in sterol composition, from ergosterol to fecosterol, caused by mutations in the C-5 sterol desaturase gene, and increased expression of genes involved in sterol biosynthesis. Additionally, large chromosome III rearrangements and mutations in genes associated with DNA damage and respiration were found, but contributed less to the thermotolerant phenotype.
authors.affiliation: Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology, SE-41296 Gothenburg, Sweden.
authors.forename: Luis
authors.initials: L
authors.lastname: Caspeta
authors.affiliation: Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology, SE-41296 Gothenburg, Sweden.
authors.forename: Yun
authors.initials: Y
authors.lastname: Chen
authors.affiliation: Department of Chemical and Biological Engineering, Chalmers Unversity of Technology, SE-41296 Gothenburg, Sweden.
authors.forename: Payam
authors.initials: P
authors.lastname: Ghiaci
authors.affiliation: Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology, SE-41296 Gothenburg, Sweden.
authors.forename: Amir
authors.initials: A
authors.lastname: Feizi
authors.affiliation: Novozymes, Analytical Science, DK-4400 Kalundborg, Denmark.
authors.forename: Steen
authors.initials: S
authors.lastname: Buskov
authors.affiliation: Science for Life Laboratory, Royal Institute of Technology, SE-17121 Stockholm, Sweden.
authors.forename: Björn M
authors.initials: BM
authors.lastname: Hallström
authors.affiliation: Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology, SE-41296 Gothenburg, Sweden. Department of Chemical and Biological Engineering, Chalmers Unversity of Technology, SE-41296 Gothenburg, Sweden.
authors.forename: Dina
authors.initials: D
authors.lastname: Petranovic
authors.affiliation: Novo Nordisk Foundation Center for Biosustainability, Chalmers University of Technology, SE-41296 Gothenburg, Sweden. Department of Chemical and Biological Engineering, Chalmers Unversity of Technology, SE-41296 Gothenburg, Sweden. Novo Nordisk Foundation Center for Biosustainability, DK-2970 Hørsholm, Denmark. nielsenj@chalmers.se.
authors.forename: Jens
authors.initials: J
authors.lastname: Nielsen
mesh_terms: D056804:Biofuels; D015825:Chromosomes, Fungal / Q000235:genetics; D004249:DNA Damage / Q000235:genetics; D019020:Directed Molecular Evolution; D004875:Ergosterol / Q000031:analogs & derivatives* / Q000096:biosynthesis / Q000737:chemistry / Q000235:genetics; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation / Q000235:genetics*; D015966:Gene Expression Regulation, Fungal; D016681:Genome, Fungal / Q000235:genetics; D006358:Hot Temperature; D009154:Mutation; D010088:Oxidoreductases / Q000235:genetics* / Q000378:metabolism; D011995:Recombination, Genetic; D012441:Saccharomyces cerevisiae / Q000201:enzymology* / Q000235:genetics / Q000254:growth & development; D017422:Sequence Analysis, DNA
chemical_list: D056804:Biofuels; D000431:Ethanol; C039241:fecosterol; D010088:Oxidoreductases; C039306:sterol delta-5 desaturase; D004875:Ergosterol