13-09: Simultaneous saccharification and fermentation of steam-pretreated corn stover using xylose-fermenting yeast

Bioethanol can be produced from sugar, starch or lignocellulosic material. Today bioethanol is mainly produced from sugar as sugar canes and starch as corn and wheat. Using lignocellulosic material, such as wood and agricultural residues, rather than sugar and starch has the advantage of minimizing the conflict between using land for food production and energy feedstock production. Corn stover is a low cost agricultural residue which is available in large quantities. Corn stover consists mainly of cellulose but also a considerable amount of hemicellulose, mainly xylose. To also use the hemicellulose for ethanol production, modified micro-organisms are needed since the wild-type S. cerevisiae cannot ferment pentoses. An efficient high pentose uptake is difficult to obtain due to high glucose and inhibitor concentrations. In this study steam-pretreated corn stover with 1% acetic acid as catalyst was investigated in simultaneous saccharification and fermentation (SSF) and the genetically modified xylose-fermenting yeast S. cerevisiae KE6-12. The yeast was adapted by cultivation on the liquid fraction of pretreated corn stover. Different process configurations and conditions of SSF were investigated, e.g., batch and fed batch, temperature and pH to increase the xylose conversion. An alternative approach is to utilize the pentose fraction for biogas production, which is also investigated. Results from this study will be presented.