Tuesday, May 3, 2011
Budi Juliman Hidayat1, Lisbeth Thygesen1 and Lennart Salmén2, (1)Danish Center for Forest and Landscape, Faculty of Life Sciences, University of Copenhagen, Frederiksberg C, Denmark, (2)Innventia, Stockholm, Sweden
In a recent study (Thygesen et al. 2010) we discussed the role of dislocations during the initial part of enzymatic hydrolysis of cellulose in plant cell walls. Dislocations are interesting within the context of biorefining and cellulosic bioethanol as they appear to be entry points for endoglucanases. Dislocations differ from the surrounding cell wall, but their exact structure remains unknown. In the present study we studied plant cell walls using Infrared microspectroscopy in an attempt to find possible differences between dislocations and the bulk cell wall. The spectra did not indicate any differences neither in chemistry, nor in crystallinity, thus confirming our earlier result that dislocations do not contain amorphous cellulose.
Using polarized infrared spectroscopy we also explored the orientation of the polymers within the cell wall (Stevanic and Salmén 2009). Micrographs of severe dislocations shown in Terziev et al. (2005) indicate that the whole cell wall buckles. It therefore seems likely that the microfibril angle is higher in dislocations than in the surrounding cell wall, and this should reflect upon the polymer orientation. However, neither in this case did the results reveal any differences between dislocations and the bulk cell wall.
The spatial resolution of our measurements was 6.25 x 6.25 μm. There is consequently a risk that spectra assigned to dislocations in reality contained information also from the surrounding cell wall. Another factor possibly contributing to such mixing is that measurements were performed in transmission and thus contain information from both the upper and the lower cell wall.
