Enhancing the Fermentability of Steam-Exploded Corn Stover Prehydrolyzate by Sulfite Detoxification

摘要

The inhibitors derived from degradation of lignocellulose make adverse impact on fermentation, which is considered as a fundamental problem in the second generation bioethanol production. To fully utilize the lignocellulosic materials, steam-exploded corn stover prehydrolyzate was fermented by Pichia stipitis CBS 5776 in this study. Effect of initial inoculum size on improving the fermentability of prehydrolyzate was investigated, which demonstrated the necessity of detoxification. Reducing agents were employed to detoxify the steam-exploded prehydrolyzate. Sulfite was found to be the effective chemical to enhance the fermentability of the prehydrolyzate. Fermentations of prehydrolyzate treated with varied sulfite loadings were carried out to find an optimal sulfite dosage in detoxification, and 10 mM sulfite was proved to be effective. The sugar utilization rate in fermentation increased significantly after the sulfite treatment, compared with the untreated prehydrolyzate. The residual xylose reduced from 24.35 g/l to 5.87 g/l and the produced ethanol increased from 11.53 g/l to 20.58 g/l at 36 h of fermentation. The mechanism of sulfite detoxification was also discussed in this work. The results indicated that sulfite treatment probably acted on the lignin degradation products, which contributed to the increase in fermentability of steam-exploded prehydrolyzate.