New Approach to Fuelization of Herbaceous Lignocelluloses through Simultaneous Saccharification and Fermentation Followed by Photocatalytic Reforming
Bio-fuelization of herbaceous lignocelluloses through a simultaneous saccharification and fermentation process (SSF) and photocatalytic reforming (photo-Reform) was examined. The SSF of the alkali-pretreated bamboo, rice straw, and silvergrass was performed in an acetate buffer (pH 5.0) using cellulase, xylanase, and Saccharomyces cerevisiae at 34 °C. Ethanol was produced in 63%-85% yields, while xylose was produced in 74%-97% yields without being fermented because xylose cannot be fermented by S. cerevisiae. After the removal of ethanol from the aqueous SSF solution, the SSF solution was subjected to a photo-Reform step where xylose was transformed into hydrogen by a photocatalytic reaction using Pt-loaded TiO2 (2 wt % of Pt content) under irradiation by a high pressure mercury lamp. The photo-Reform process produced hydrogen in nearly a yield of ten theoretical equivalents to xylose. Total energy was recovered as ethanol and hydrogen whose combustion energy was 73.4%-91.1% of that of the alkali-pretreated lignocelluloses (holocellulose).