title: Time-based comparative transcriptomics in engineered xylose-utilizing Saccharomyces cerevisiae identifies temperature-responsive genes during ethanol production.
abstract: Agricultural residues comprising lignocellulosic materials are excellent sources of pentose sugar, which can be converted to ethanol as fuel. Ethanol production via consolidated bioprocessing requires a suitable microorganism to withstand the harsh fermentation environment of high temperature, high ethanol concentration, and exposure to inhibitors. We genetically enhanced an industrial Saccharomyces cerevisiae strain, sun049, enabling it to uptake xylose as the sole carbon source at high fermentation temperature. This strain was able to produce 13.9 g/l ethanol from 50 g/l xylose at 38 °C. To better understand the xylose consumption ability during long-term, high-temperature conditions, we compared by transcriptomics two fermentation conditions: high temperature (38 °C) and control temperature (30 °C) during the first 12 h of fermentation. This is the first long-term, time-based transcriptomics approach, and it allowed us to discover the role of heat-responsive genes when xylose is the sole carbon source. The results suggest that genes related to amino acid, cell wall, and ribosomal protein synthesis are down-regulated under heat stress. To allow cell stability and continuous xylose uptake in order to produce ethanol, hexose transporter HXT5, heat shock proteins, ubiquitin proteins, and proteolysis were all induced at high temperature. We also speculate that the strong relationship between high temperature and increased xylitol accumulation represents the cell's mechanism to protect itself from heat degradation.
authors.affiliation: Department of Chemical Science and Engineering, Graduate School of Engineering, Kobe University, 1-1 Rokkodai-cho, Nada, Kobe, 657-8501, Japan.
authors.forename: Ku Syahidah Ku
authors.initials: KS
authors.lastname: Ismail
authors.forename: Takatoshi
authors.initials: T
authors.lastname: Sakamoto
authors.forename: Tomohisa
authors.initials: T
authors.lastname: Hasunuma
authors.forename: Akihiko
authors.initials: A
authors.lastname: Kondo
mesh_terms: D002473:Cell Wall / Q000235:genetics / Q000378:metabolism; D000431:Ethanol / Q000378:metabolism*; D005285:Fermentation; D020869:Gene Expression Profiling; D015966:Gene Expression Regulation, Fungal; D005800:Genes, Fungal / Q000235:genetics; D006360:Heat-Shock Proteins / Q000096:biosynthesis / Q000235:genetics; D006358:Hot Temperature; D060847:Metabolic Engineering; D009004:Monosaccharide Transport Proteins / Q000096:biosynthesis / Q000235:genetics; D005810:Multigene Family / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D015203:Reproducibility of Results; D012269:Ribosomal Proteins / Q000096:biosynthesis / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics* / Q000378:metabolism*; D029701:Saccharomyces cerevisiae Proteins / Q000096:biosynthesis / Q000235:genetics; D013696:Temperature; D013997:Time Factors; D059467:Transcriptome / Q000235:genetics*; D025801:Ubiquitin / Q000096:biosynthesis / Q000235:genetics; D014993:Xylitol / Q000096:biosynthesis / Q000378:metabolism; D014994:Xylose / Q000378:metabolism*
chemical_list: C466910:HXT5 protein, S cerevisiae; D006360:Heat-Shock Proteins; D009004:Monosaccharide Transport Proteins; D012269:Ribosomal Proteins; D029701:Saccharomyces cerevisiae Proteins; D025801:Ubiquitin; D000431:Ethanol; D014994:Xylose; D014993:Xylitol