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Biofuels. Altered sterol composition renders yeast thermotolerant.

Science (New York, N.Y.) (2014-10-04)
Luis Caspeta, Yun Chen, Payam Ghiaci, Amir Feizi, Steen Buskov, Björn M Hallström, Dina Petranovic, Jens Nielsen
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.

MATERIALS
Product Number
Brand
Product Description

Supelco
Ethanol solution, certified reference material, 2000 μg/mL in methanol
Sigma-Aldrich
Reagent Alcohol, anhydrous, ≤0.003% water
Sigma-Aldrich
Reagent Alcohol, anhydrous, ≤0.005% water
Supelco
Ethanol-20 (10 ampules/kit), 20 mg/dL in H2O, ampule of 10 × 1.2 mL, certified reference material, Cerilliant®
Supelco
Ethanol-500, 500 mg/dL in H2O, ampule of 10 × 1.2 mL, certified reference material, Cerilliant®
Supelco
Ethanol-400 (10 ampules/kit), 400 mg/dL in H2O, ampule of 10 × 1.2 mL, certified reference material, Cerilliant®
USP
Dehydrated Alcohol, United States Pharmacopeia (USP) Reference Standard
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Ethanol Calibration Kit, ampule of 10 × 1.2 mL, certified reference material, Cerilliant®
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Ethanol-25, 25 mg/dL in H2O, ampule of 10 × 1.2 mL, certified reference material, Cerilliant®
Sigma-Aldrich
Ergosterol, ≥75%
Supelco
Ethanol-40, 40 mg/dL in H2O, ampule of 10 × 1.2 mL, certified reference material, Cerilliant®
Supelco
Ethanol-10, 10 mg/dL in H2O, pack of 10 × 1.2 mL ampules, certified reference material, Cerilliant®
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Ethanol-150, 150 mg/dL in H2O, ampule of 10 × 1.2 mL, certified reference material, Cerilliant®
Supelco
Ethanol-50, 50 mg/dL in H2O, ampule of 10 × 1.2 mL, certified reference material, Cerilliant®
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Ethyl alcohol, Pure, 190 proof, for molecular biology
Ergosterol, European Pharmacopoeia (EP) Reference Standard
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Ethanol-200 (10 ampules/kit), 200 mg/dL in H2O, ampule of 10 × 1.2 mL, certified reference material, Cerilliant®
Supelco
Ethanol-80, 80 mg/dL in H2O, ampule of 10 × 1.2 mL, certified reference material, Cerilliant®
Supelco
Ethanol-100 (10 ampules/kit), 100 mg/dL in H2O, ampule of 10 × 1.2 mL, certified reference material, Cerilliant®
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Ethanol-300, 300 mg/dL in H2O, ampule of 10 × 1.2 mL, certified reference material, Cerilliant®
Sigma-Aldrich
Ethyl alcohol, Pure, 200 proof, ACS reagent, ≥99.5%