Bioethanol production based on simultaneous saccharification and fermentation of steam-pretreated Salix at high dry-matter content

Simultaneous saccharification and fermentation (SSF) was performed on the slurries resulting from steam pretreatment of non-, SO2- and H2SO4-impregnated Salix chips. The aim was to increase the ethanol concentration by running SSF at high dry-matter content, while maintaining a high ethanol yield. Using SO2-impregnated Salix chips in steam pretreatment resulted in the highest ethanol concentration in the subsequent SSF. At a water-insoluble solids concentration of 9%, 32 g/L ethanol was obtained after 78 h of SSF, using 3.3 g/L baker's yeast (Saccharomyces cerevisiae) cultivated on the pretreatment liquid. This corresponds to an overall ethanol yield of 76% of the theoretical, based on the glucan and mannan content in the raw material. The cultivation procedure made the yeast better adapted to the medium. However, increasing the substrate loading further resulted in decreased fermentability.