title: Re-assessment of YAP1 and MCR1 contributions to inhibitor tolerance in robust engineered Saccharomyces cerevisiae fermenting undetoxified lignocellulosic hydrolysate.
abstract: Development of robust yeast strains that can efficiently ferment lignocellulose-based feedstocks is one of the requirements for achieving economically feasible bioethanol production processes. With this goal, several genes have been identified as promising candidates to confer improved tolerance to S. cerevisiae. In most of the cases, however, the evaluation of the genetic modification was performed only in laboratory strains, that is, in strains that are known to be quite sensitive to various types of stresses. In the present study, we evaluated the effects of overexpressing genes encoding the transcription factor (YAP1) and the mitochondrial NADH-cytochrome b5 reductase (MCR1), either alone or in combination, in an already robust and xylose-consuming industrial strain of S. cerevisiae and evaluated the effect during the fermentation of undiluted and undetoxified spruce hydrolysate. Overexpression of either gene resulted in faster hexose catabolism, but no cumulative effect was observed with the simultaneous overexpression. The improved phenotype of MCR1 overexpression appeared to be related, at least in part, to a faster furaldehyde reduction capacity, indicating that this reductase may have a wider substrate range than previously reported. Unexpectedly a decreased xylose fermentation rate was also observed in YAP1 overexpressing strains and possible reasons behind this phenotype are discussed.
authors.affiliation: Applied Microbiology, Department of Chemistry, Lund University, P.O. Box 124, Lund, SE-22100, Sweden.
authors.forename: Valeria
authors.initials: V
authors.lastname: Wallace-Salinas
authors.affiliation: University of Milano Bicocca, Piazza della Scienza 2, Milan, 20126, Italy.
authors.forename: Lorenzo
authors.initials: L
authors.lastname: Signori
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, Leuven, KU, Belgium ; Department of Molecular Microbiology, VIB, Kasteelpark Arenberg 31, Leuven, Heverlee, B-3001, Flanders, Belgium.
authors.forename: Ying-Ying
authors.initials: YY
authors.lastname: Li
authors.affiliation: Department of Chemical and Biological Engineering, Industrial Biotechnology, Chalmers University of Technology, Gothenburg, SE-41296, Sweden.
authors.forename: Magnus
authors.initials: M
authors.lastname: Ask
authors.affiliation: Department of Chemical and Biological Engineering, Industrial Biotechnology, Chalmers University of Technology, Gothenburg, SE-41296, Sweden.
authors.forename: Maurizio
authors.initials: M
authors.lastname: Bettiga
authors.affiliation: University of Milano Bicocca, Piazza della Scienza 2, Milan, 20126, Italy.
authors.forename: Danilo
authors.initials: D
authors.lastname: Porro
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, Leuven, KU, Belgium ; Department of Molecular Microbiology, VIB, Kasteelpark Arenberg 31, Leuven, Heverlee, B-3001, Flanders, Belgium.
authors.forename: Johan M
authors.initials: JM
authors.lastname: Thevelein
authors.affiliation: University of Milano Bicocca, Piazza della Scienza 2, Milan, 20126, Italy.
authors.forename: Paola
authors.initials: P
authors.lastname: Branduardi
authors.affiliation: Laboratory of Molecular Cell Biology, Institute of Botany and Microbiology, Leuven, KU, Belgium ; Department of Molecular Microbiology, VIB, Kasteelpark Arenberg 31, Leuven, Heverlee, B-3001, Flanders, Belgium.
authors.forename: María R
authors.initials: MR
authors.lastname: Foulquié-Moreno
authors.affiliation: Applied Microbiology, Department of Chemistry, Lund University, P.O. Box 124, Lund, SE-22100, Sweden.
authors.forename: Marie
authors.initials: M
authors.lastname: Gorwa-Grauslund
keywords: Ethanol; Hydrolysate; Inhibitors; MCR1; Saccharomyces cerevisiae; YAP1