An iTRAQ Based Comparative Proteomic Profiling of Thermotolerant Saccharomyces cerevisiae JRC6 in Response to High Temperature Fermentation

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 degrees C) and high temperature (40 degrees 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 bio-molecules, cell division, etc. were identified. Cells grown at 40 degrees C showed many-fold increase in the expression for many proteins involved in different functions specially biosynthesis, heat stress and metabolism. At 40 degrees C heat shock proteins (78), prefoldin subunit (6), DNA binding protein SNT1, J type co-chaperone JAC1, elongation factor 1-beta, glutathione synthase, malate synthase (2), purine biosynthesis protein ADE17, SSD1 protein, alcohol dehydrogenase 1, 3, 60S ribosomal protein L35-B, mitochondrial import protein MASS 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.