Cell-wall structural changes in wheat straw pretreated for bioethanol production

Jan B Kristensen¹ , Lisbeth G Thygesen¹ , Claus Felby¹ , Henning Jørgensen¹ and Thomas Elder²

¹Forest and Landscape Denmark, University of Copenhagen, Rolighedsvej 23, DK-1958 Frederiksberg, Denmark

²Utilization of Southern Forest Products, USDA-Forest Service, Southern Research Station, Shreveport Highway, Pineville, LA 71360, USA

author email corresponding author email

Biotechnology for Biofuels 2008, 1:5doi:10.1186/1754-6834-1-5


Published:	16 April 2008

Abstract

Background

Pretreatment is an essential step in the enzymatic hydrolysis of biomass and subsequent production of bioethanol. Recent results indicate that only a mild pretreatment is necessary in an industrial, economically feasible system. The Integrated Biomass Utilisation System hydrothermal pretreatment process has previously been shown to be effective in preparing wheat straw for these processes without the application of additional chemicals. In the current work, the effect of the pretreatment on the straw cell-wall matrix and its components are characterised microscopically (atomic force microscopy and scanning electron microscopy) and spectroscopically (attenuated total reflectance Fourier transform infrared spectroscopy) in order to understand this increase in digestibility.

Results

The hydrothermal pretreatment does not degrade the fibrillar structure of cellulose but causes profound lignin re-localisation. Results from the current work indicate that wax has been removed and hemicellulose has been partially removed. Similar changes were found in wheat straw pretreated by steam explosion.

Conclusion

Results indicate that hydrothermal pretreatment increases the digestibility by increasing the accessibility of the cellulose through a re-localisation of lignin and a partial removal of hemicellulose, rather than by disruption of the cell wall.