Grant: NSERC/Energy Sector, Natural Resources Canada

Under the Kyoto Accord which came into effect on February 16, 2005, Canada is committed to reduce the emission of greenhouse gases (GHGs) to 6% below 1990 levels during 2008-2012.  One way to do so is to decrease GHG emission from the transportation sector which is the primary source (about 25%) of the total GHG emission in Canada and US.  By substituting or blending gasoline with cleaner burning fuels such as ethanol, GHG emissions can be reduced significantly.  Increasing use of ethanol can also reduce our dependence on non-renewable fossil fuels.  Lignocellulosic plant biomass is one of the most attractive feedstocks in the medium to long term for conversion to fuel ethanol.  To improve the economics of this process, all the hexoses and pentoses in plant biomass must be converted efficiently to ethanol.  Pentose -fermenting yeasts can ferment the major sugars in lignocellulose hydrolysates into ethanol.  However, they suffer from glucose repression and low ethanol tolerance, and are susceptible to various inhibitors in lignocellulosic hydrolysates or waste liquors of pulp- or paper-processing plants.  We propose to use a novel genome shuffling method to generate mutants of yeasts such as Pachysolen tannophilus, Pichia stipitis and metabolically engineered Saccharomyces cerivisiae with improved ability to ferment the dominant hexoses and pentoses in a pulp-processing waste liquor to ethanol.  Genome shuffling involves the generation of a pool of mutants with improved phenotypes, followed by iterative recombination between their genomes.  This method is particularly useful for improving multi-genic traits such as tolerance to hydrolysate inhibitors and ethanol being sought in the proposed study.  We will be aided by Stephen del Cardayré of Belmont, California who developed the genome shuffling method.  We will also work closely with Michael Paice (PAPRICAN, Montréal, QC) and Juraj Strmen (Tembec, Témiscaming, QC) who will provide spent sulfite liquor (SSL), SSL-adapted test strain and some equipment for our studies.  Successful undertaking of this research will yield improved yeasts able to efficiently ferment the hexoses and pentoses in lignocellulose hydrolysates to ethanol.