Whole-cell gene and protein expression profilings of saccharomyces cerevisiae grown under different gravity environments

二氧化碳（CO2）的失衡一直被认为是全球变暖的主要原因。人们提出了许多减少二氧化碳排放的方法。用乙醇代替部分汽油是一种很有前途的方法。对现有的乙醇生产工艺稍加修改，就可以使用高糖含量的底物。然而，饲喂含糖量高的底物并不能保证乙醇产量高，反而会导致酵母细胞死亡。这种不良结果归因于高糖浓度的渗透作用和高乙醇浓度的抑制作用的综合作用。造成这种不良后果的具体原因尚不清楚。2005年全球乙醇产量接近140亿升。乙醇产量每提高1%就能带来数千万美元的利润。因此，高乙醇产量的生产工艺是受欢迎的。本研究的目的是研究酵母细胞在不同重力条件下的活性、功能和活力；特别是在非常高重力的环境下（例如，250克葡萄糖/升）。当代分子生物学方法将用于研究全细胞基因表达和蛋白质表达谱的商业酵母菌株。该菌株将在类似于工业过程中使用的不同条件下培养。采集的样品将使用微阵列技术和串联质谱分析。随着测量的代谢物浓度，基因和蛋白质信息将通过代谢通量分析结合和整合。从通量分析中提取的生物信息将用于设计适当的培养策略，随后将在开发高乙醇产量和高利润的发酵工艺中实施。

Imbalance of carbon dioxide (CO2) has been considered as the major cause of global warming. Many approaches to reducing CO2 emission have been proposed. Using ethanol to replace a portion of gasoline is one of the promising approaches. With a slight modification of the existing ethanol production process, using a high sugar-content substrate becomes possible. However, feeding with a high sugar-content substrate does not guarantee high ethanol yield, but would lead to yeast cell death. Such an adverse result is attributed to a combined osmotic effect due to high sugar concentration and inhibitory effect due to high ethanol level. The detailed cause of such an adverse outcome is still unclear. The global ethanol production in 2005 was nearly 14 billion liters. A one-percent increase in ethanol productivity would translate to tens of million of dollars in profit. Thus a high ethanol-yield production process is welcome.  The objective of this proposal is to study the yeast cellular activity, function, and viability at different gravity conditions; particularly in a very-high-gravity environment (i.e., > 250 g glucose/l). Contemporary molecular biology approaches will be used to investigate whole-cell gene expression and protein expression profiling of a commercial yeast strain. The strain will be cultivated under different conditions similar to those used in industrial processes. The harvested samples will be analyzed using microarray technology and tandem mass spectrometry. Along with measured metabolite concentrations, gene and protein information will be combined and integrated by means of metabolic flux analysis. The biological information extracted from flux analysis will be used to design a proper cultivation strategy, which will be subsequently implemented in the development of a high ethanol-yield and a high-profit fermentation process.