Sunday, May 3, 2009
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Dilute-acid pretreatment of rice straw at bench-scale using extrusion and extraction process to improve concentration and conversion of xylose in lignocellulosic hydrolysate for bioethanol production

Wen-Hua Chen, Ting-Hsiang Lin, and Jia-Baau Wang. Cellulosic Ethanol Program, Institute of Nuclear Energy Research, No. 1000, Wenhua Road, Jiaan Village, Longtan, Taoyuan, 32546, Taiwan

    In a typical process for producing bioethanol, pretreatment of lignocellulosic material is required to extract xylose that microorganisms can ferment to ethanol from hemicellulose. Diluted-acid pretreatment can increase the yield of the carbohydrates from the hemicellulose, and is therefore the most popular method. Considering equipment cost and energy consumed in the distillation, increasing the concentration and conversion of xylose in the hydrolysate during the dilute-acid pretreatment is a specific item to be investigated. In this study, a bench-scale biomass pretreatment process that applied on 10 kg rice straw /batch system was installed and developed to achieve above mentioned goal at Institute of Nuclear Energy Research (INER) in Taiwan. The pretreatment process includes the step of extruding and mixing with acid and the step of hot water to extraction xylose from hemicellulose. The results show that the optimum conditions for twin-screw extruder were 40 rpm screw speed, 120oC extrusion temperature, and 3% acid concentration, while for hot water extraction were 20 min reaction time and 130oC reaction temperature. Under these conditions xylose concentration and conversion reached 50-60 gL-1 and 80-90%, respectively. The glucose conversions generally were lower than 10%. Moreover, xylose in the obtained rice straw hydrolysate was successful fermented to ethanol using a Pichia stipitis even at high acetic acid concentration present in the hydrolysate. The ethanol yield was achieved 0.43-0.47 gp gs-1, equivalent to 87-93% of the maximal ethanol conversion.

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See more of The 31st Symposium on Biotechnology for Fuels and Chemicals (May 3-6, 2009)