Conference Dates

March 8-13, 2009


Different lignocellulosic materials, from e.g. forest industry and agriculture, are potentially interesting feedstocks for ethanol production. To meet desired overall yields during ethanol production from lignocellulosic materials, it is important to use both hexoses and pentoses. Saccharomyces cerevisiae, the most commonly used organism for industrial ethanol production, does not naturally ferment pentoses. Currently, genetically modified Saccharomyces cerevisiae strains are becoming available for xylose fermentation. However, simultaneous fermentation of xylose and glucose in genetically modified Saccharomyces cerevisiae requires a favorable ratio between these sugars.

In simultaneous saccharification and fermentation (SSF) of spruce, a potential feedstock in the northern hemisphere, the proportion of xylose is relatively low. Still, conversion of all xylose would increase the ethanol yield by as much as 7-8%. However, the low ratio between xylose and glucose makes this conversion challenging. Hence, a suitable process design for simultaneous saccharification and co-fermentation (SSCF) is needed.

In xylose rich materials, such as wheat straw, there is a more favorable ratio of xylose and glucose. On the other hand, there are indications that the residual xylose after fermentation is higher for these feedstocks. Consequently, there is a need for improved process design also in this case.

In the present work studies of enzyme kinetics and consumption rates were carried out in order to create a model for sugar release and sugar uptake. An improved SSCF process was subsequently designed on the basis of this model and experimentally verified.