Diniz Raphael Hermano Santos, Villada Juan C, Alvim Mariana Caroline Tocantins, Vidigal Pedro Marcus Pereira, Vieira Nívea Moreira, Lamas-Maceiras Mónica, Cerdán María Esperanza, González-Siso María-Isabel, Lahtvee Petri-Jaan, da Silveira Wendel Batista
Laboratory of Microbial Physiology, Department of Microbiology, Universidade Federal de Viçosa, Vicosa, MG, Brazil.
Center for Analysis of Biomolecules, Center for Biological and Health Sciences, Universidade Federal de Viçosa, Vicosa, MG, Brazil.
Appl Microbiol Biotechnol. 2017 Sep;101(18):6969-6980. doi: 10.1007/s00253-017-8432-0. Epub 2017 Aug 3.
The thermotolerant yeast Kluyveromyces marxianus displays a potential to be used for ethanol production from both whey and lignocellulosic biomass at elevated temperatures, which is highly alluring to reduce the cost of the bioprocess. Nevertheless, contrary to Saccharomyces cerevisiae, K. marxianus cannot tolerate high ethanol concentrations. We report the transcriptional profile alterations in K. marxianus under ethanol stress in order to gain insights about mechanisms involved with ethanol response. Time-dependent changes have been characterized under the exposure of 6% ethanol and compared with the unstressed cells prior to the ethanol addition. Our results reveal that the metabolic flow through the central metabolic pathways is impaired under the applied ethanol stress. Consistent with these results, we also observe that genes involved with ribosome biogenesis are downregulated and gene-encoding heat shock proteins are upregulated. Remarkably, the expression of some gene-encoding enzymes related to unsaturated fatty acid and ergosterol biosynthesis decreases upon ethanol exposure, and free fatty acid and ergosterol measurements demonstrate that their content in K. marxianus does not change under this stress. These results are in contrast to the increase previously reported with S. cerevisiae subjected to ethanol stress and suggest that the restructuration of K. marxianus membrane composition differs in the two yeasts which gives important clues to understand the low ethanol tolerance of K. marxianus compared to S. cerevisiae.
耐热酵母马克斯克鲁维酵母显示出在高温下用于从乳清和木质纤维素生物质生产乙醇的潜力，这对于降低生物过程的成本极具吸引力。然而，与酿酒酵母不同，马克斯克鲁维酵母不能耐受高浓度乙醇。我们报告了马克斯克鲁维酵母在乙醇胁迫下的转录谱变化，以便深入了解与乙醇反应相关的机制。在6%乙醇暴露下对时间依赖性变化进行了表征，并与添加乙醇前的未受胁迫细胞进行了比较。我们的结果表明，在所施加的乙醇胁迫下，通过中心代谢途径的代谢流受到损害。与这些结果一致，我们还观察到参与核糖体生物合成的基因下调，而编码热休克蛋白的基因上调。值得注意的是，一些与不饱和脂肪酸和麦角固醇生物合成相关的编码酶的基因表达在乙醇暴露后下降，游离脂肪酸和麦角固醇的测量表明它们在马克斯克鲁维酵母中的含量在这种胁迫下没有变化。这些结果与先前报道的乙醇胁迫下酿酒酵母的增加形成对比，表明马克斯克鲁维酵母膜组成的重组在两种酵母中有所不同，这为理解马克斯克鲁维酵母与酿酒酵母相比乙醇耐受性低提供了重要线索。
