초록
In this study, nitric acid (HNO<SUB>3</SUB>) was evaluated as an acid catalyst for rice straw pretreatment, and, after neutralization, as a sole nitrogen source for subsequent fermentation. Response surface methodology was used to obtain optimal pretreatment condition with respect to HNO<SUB>3</SUB> concentration (0.2-1.0%), temperature (120-160<SUP>o</SUP>C) and reaction time (1-20min). In a condition of 0.65% HNO<SUB>3</SUB>, 158.8<SUP>o</SUP>C and 5.86min, a maximum xylose yield of 86.5% and an enzymatic digestibility of 83.0% were achieved. The sugar solution that contained nitrate derived from the acid catalyst supported the enhancement of ethanol yield by Pichia stipitis from 10.92g/L to 14.50g/L. The results clearly reveal that nitric acid could be used not only as a pretreatment catalyst, but also as a nitrogen source in the fermentation process for bioethanol production. It is anticipated that the HNO<SUB>3</SUB>-based pretreatment can reduce financial burden on the cellulosic bioethanol industry by simplifying after-pretreatment-steps as well as providing a nitrogen source.