title: Overexpression of the yeast transcription activator Msn2 confers furfural resistance and increases the initial fermentation rate in ethanol production.
abstract: Lignocellulosic biomass is a promising source for bioethanol production, because it is abundant worldwide and has few competing uses. However, the treatment of lignocelllulosic biomass with weak acid to release cellulose and hemicellulose generates many kinds of byproducts including furfural and 5-hydroxymethylfurfural, which inhibit fermentation by yeast, because they generate reactive oxygen species (ROS) in cells. In order to acquire high tolerance to oxidative stress in bioethanol yeast strains, we focused on the transcription activator Msn2 of Saccharomyces cerevisiae, which regulates numerous genes involved in antioxidative stress responses, and constructed bioethanol yeast strains that overexpress Msn2 constitutively. The Msn2-overexpressing bioethanol strains showed tolerance to oxidative stress, probably due to the high-level expression of various antioxidant enzyme genes. Unexpectedly, these strains showed ethanol sensitivity compared with the control strain, probably due to imbalance of the expression level between Msn2 and Msn4. In the presence of furfural, the engineered strains exhibited reduced intracellular ROS levels, and showed rapid growth compared with the control strain. The fermentation test in the presence of furfural revealed that the Msn2-overexpressing strains showed improvement of the initial rate of fermentation. Our results indicate that overexpression of the transcription activator Msn2 in bioethanol yeast strains confers furfural tolerance by reducing the intracellular ROS levels and enhances the initial rate of fermentation in the presence of furfural, suggesting that these strains are capable of adapting rapidly to various compounds that inhibit fermentation by inducing ROS accumulation. Our results not only promise to improve bioethanol production from lignocellulosic biomass, but also provide novel insights for molecular breeding of industrial yeast strains.
authors.affiliation: Graduate School of Biological Sciences, Nara Institute of Science and Technology, 8916-5 Takayama, Ikoma, Nara 630-0192, Japan.
authors.forename: Yu
authors.initials: Y
authors.lastname: Sasano
authors.forename: Daisuke
authors.initials: D
authors.lastname: Watanabe
authors.forename: Ken
authors.initials: K
authors.lastname: Ukibe
authors.forename: Tomomi
authors.initials: T
authors.lastname: Inai
authors.forename: Iwao
authors.initials: I
authors.lastname: Ohtsu
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Shimoi
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Takagi
mesh_terms: D002482:Cellulose / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D004351:Drug Resistance / Q000235:genetics*; D000431:Ethanol; D005285:Fermentation / Q000235:genetics*; D005662:Furaldehyde / Q000633:toxicity*; D015870:Gene Expression; D007218:Industrial Microbiology; D018384:Oxidative Stress / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000187:drug effects* / Q000201:enzymology / Q000235:genetics* / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics* / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; C081935:MSN2 protein, S cerevisiae; D017382:Reactive Oxygen Species; D029701:Saccharomyces cerevisiae Proteins; D014157:Transcription Factors; D000431:Ethanol; D002482:Cellulose; D005662:Furaldehyde