Sunday, April 29, 2007

Mixed sugars fermentation performances of an arabinose/xylose fermenting Saccharomyces cerevisiae strain expressing xylose isomerase

Maurizio Bettiga, Kaisa Karhumaa, Rosa Garcia-Sanchez, Bärbel Hahn-Hägerdal, and Marie F. Gorwa-Grauslund. Applied Microbiology, Lund University, PO Box 124, SE-22100, Lund, Sweden

Fuel ethanol could be produced in a sustainable way by bioconversion of lignocellulosic biomass from forestry and agricultural raw materials. Baker’s yeast Saccharomyces cerevisiae is the prime choice for the fermentative production of bioethanol. This yeast is able to rapidly convert hexose sugars to ethanol, with high yield and high productivity. Moreover, it is adapted to high ethanol concentrations and it displays a good tolerance to several fermentation-inhibiting compounds present in lignocellulosic derived media. However, S. cerevisiae is not naturally able to utilize xylose and arabinose, which may constitute a significant portion of the lignocellulosic feedstock. Since maximal feedstock utilisation is essential for economic competitiveness, the feasibility of the forthcoming switch from fossil fuels to biofuels is strongly dependent on the development of a biocatalyst with a broad range of substrates.

Bacterial arabinose utilization pathway has previously been combined with the xylose reductase/xylitol dehydrogenase xylose utilisation pathway, both in laboratory and industrial strains of S. cerevisiae. In the present study we report the evaluation of mixed sugars fermentation of arabinose consuming strains in which a pathway for xylose assimilation based on xylose isomerase was introduced.