Background: Bioethanol derived from lignocellulosic biomass can supplement the ethanol supplies in a sustainable manner. However, the bioethanol production process is still not cost effective and researchers are looking for novel strategies like simultaneous saccharification fermentation to cut down the production cost. Thermotolerant yeast Saccharomyces cerevisiae JRC6 is reported to improve the fermentation efficiency under SSF. However, the mechanism of thermotolerance of the strain is unknown which is important for developing more robust yeast strains for simultaneous saccharification and fermentation.

Objective: To identify proteomic changes responsible for imparting thermotolerance by iTRAQ based profiling of Saccharomyces cerevisiae JRC6 by growing at optimum (30°C) and high temperature (40°C).

Methods: iTRAQ labeling followed by electrospray ionization based tandem mass spectrometry using SCIEX 5600 Triple-TOF Mass Spectrometer (MS).

Results: A total of 582 proteins involved in heat shock, metabolism, biosynthesis, transport of biomolecules, cell division, etc. were identified. Cells grown at 40°C showed many-fold increase in the expression for many proteins involved in different functions specially biosynthesis, heat stress and metabolism. At 40°C heat shock proteins (78), prefoldin subunit (6), DNA binding protein SNT1, J type co-chaperone JAC1, elongation factor 1-β, glutathione synthase, malate synthase (2), purine biosynthesis protein ADE17, SSD1 protein, alcohol dehydrogenase 1, 3, 60S ribosomal protein L35-B, mitochondrial import protein MAS5 and many other proteins were significantly upregulated.

Conclusion: The iTRAQ analysis revealed many heat shock proteins and heat stable alcohol dehydrogenases which can be exploited to develop a more robust yeast strain suitable for simultaneous saccharification and fermentation or consolidated bioprocessing.

背景：源自木质纤维素生物质的生物乙醇可以可持续方式补充乙醇供应。然而，生物乙醇的生产过程仍不具有成本效益，研究人员正在寻找新颖的策略，例如同时糖化发酵以降低生产成本。据报道，耐热酵母酿酒酵母JRC6可提高SSF条件下的发酵效率。然而，菌株的耐热机制尚不清楚，这对于开发更健壮的酵母菌株以同时进行糖化和发酵非常重要。

目的：通过在最佳温度（30°C）和高温（40°C）下生长，鉴定基于iTRAQ的酿酒酵母JRC6的基因组学变化，从而赋予耐热性。

方法：iTRAQ标记，然后使用SCIEX 5600 Triple-TOF质谱仪（MS）进行基于电喷雾电离的串联质谱。

结果：共鉴定出582种涉及热休克，代谢，生物合成，生物分子运输，细胞分裂等的蛋白质。在40°C下生长的细胞对于参与不同功能（特别是生物合成，热应激和代谢）的许多蛋白质的表达显示出许多倍的增长。在40°C时热休克蛋白（78），前折叠蛋白亚基（6），DNA结合蛋白SNT1，J型伴侣蛋白JAC1，延伸因子1-β，谷胱甘肽合酶，苹果酸合酶（2），嘌呤生物合成蛋白ADE17，SSD1蛋白，乙醇脱氢酶1、3、60S核糖体蛋白L35-B，线粒体输入蛋白MAS5和许多其他蛋白均显着上调。

结论：iTRAQ分析揭示了许多热激蛋白和热稳定的醇脱氢酶，可以利用它们开发出更健壮的酵母菌株，适用于同时糖化和发酵或整合的生物工艺。