Project Number: 3620-41000-123-00
Project Type: Appropriated

Start Date: Sep 01, 2004
End Date: Aug 31, 2009

Objective:
Determine the metabolic, physiologic, and genetic fundamentals underlying stress tolerance of ethanologenic yeast strains and other microbes. Using this fundamental stress tolerance knowledge, engineer improved strains and/or design process conditions that foster stress tolerance and functionality of microbes for production of ethanol and bioproducts from corn fiber and other lignocellulosic materials, despite exposure to harsh environments.

Approach:
Screening for phenotype differences in stress tolerance of yeast strains will be the first step in the search for genes and gene systems fostering resilience to stress factors. Stress factors common to fermentations of lignocellulose hydrolzates will be the focus of this research, including various chemical fermentation inhibitors (furans, phenolics, organic acids, etc.), high ethanol concentration, wide pH and osmotic shifts, and the high temperatures needed for simultaneous saccharification-fermentation processes. Cultures screened will include natural ethanologenic yeasts capable of hexose and pentose fermentation, strains adapted to increasing levels of stress, an S. cerevisiae disruption mutant library, and S. cerevisiae transformants prepared using a cDNA library from a furan-resistant/detoxifying yeast. Genes responsible for observed changes in stress tolerance will be identified and characterized with respect to sequence homology, protein structural domains, and protective function. Cultural conditions (nutrition, carbon and nitrogen source/ratio/concentration, physiological cell age, osmotic pressure, pH, temperature, dissolved oxygen, and others) will also be varied to screen for shifts in stress tolerance. Quality-controlled microarrays will be designed and applied to identify genes associated with stress responses and to study the genomic response of cultures to applied stress factors during fermentation time courses in order to identify gene networks and control mechanisms involved in stress tolerance and structural domain. Genetic tools and information gained will be applied to engineer improved strains and optimize the fermentation process to foster improved stress tolerance for lower cost production of ethanol from hydrolyzates of lignocellulosic biomass. BSL-1 and Risk Group RG1 recertified April 17, 2008.