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

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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.