FWF-Enzymologie der Xylosev - Enzymology of xylose utilization in yeast

    Project: Research project

    Project Details


    A recent directive of the European Union proposed that biofuels should represent 2% of the total transportation fuel
    consumption by 2005. In order to achieve this ambitious goal, it is clearly necessary to improve the current
    biotechnologies for fuel production, particularly if non-conventional feedstocks such as lignocellulose are being
    used as raw materials. Lignocellulose is attractive because it is renewable through the process of plant
    photosynthesis and available in huge quantities as wastes from forestry, agriculture and the pulp and paper
    industries. It is composed of the polysaccharides cellulose and hemicellulose, and lignin. A number of studies have
    shown that the economics of a process for lignocellulose conversion require that efficient uses for both cellulose
    and hemicellulose be found. Glucose and xylose are the main constituent monosaccharides ('sugars') in cellulose
    and hemicellulose, respectively. While glucose can be fermented easily into alcohol, the production of ethanol
    from xylose remains a challenge. The classical brewer's or baker's yeasts are unable to utilise xylose unless
    engineered with tools of molecular biology to have extra metabolic capabilities. However, the engineered yeast
    strains often produce little ethanol, accumulating other by-products. There is a major problem leading to this
    shortcoming during xylose fermentation: NAD(P) cofactors are not recycled efficiently between the enzymes
    catalyzing the first two steps of xylose assimilation. Therefore, the development of an industrial production
    organism requires that the initial steps of xylose utilisation be optimised. Recent studies in the applicant's
    laboratory make possible a novel approach to overcome the intrinsic limitations of current recombinant strains
    designed to ferment xylose. In this project, enzymes with tailored specificities will be generated by site-directed
    mutagenesis, and mutated genes will be introduced into the genome of the yeast Saccharomyces cerevisiae. The
    organism expressing the altered genes will now be able to ferment xylose with improved yield and at a reduced
    level of by-products. The novel strains produced by metabolic engineering will be tested under fermentation
    conditions in bioreactors to provide essential information about physiology and potential industrial application.
    Effective start/end date1/10/0515/01/09


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