Monday, April 19, 2010
2-08

Multi-level evidences indicate that cellulose solvent-based pretreatment efficiently breaks the recalcitrance of switchgrass: Crystallinity or accessibility?

Noppadon Sathitsuksanoh, Zhiguang Zhu, and Y.-H. Percival Zhang. Biological Systems Engineering, Virginia Tech, 210-A Seitz Hall, Blacksburg, VA 24061

Effectively overcoming biomass recalcitrance is one of the major tasks to release soluble sugars.  Cellulose solvent- and organic solvent-based lignocellulose fractionation (COSLIF) has been shown to effectively break biomass recalcitrance under modest reaction conditions 1,2.  COSLIF was applied to pretreat switchgrass.  The glucan digestibility of the COSLIF-pretreated switchgrass was 89% at hour 36 at one filter paper unit of cellulase per gram of glucan.

Cellulose crystalinity has been widely regarded as a key substrate characteristic that affects enzymatic hydrolysis.  XRD, FT-IR, and CP/MAS 13C-NMR were utilized to determine crystallinity index (CrI) of the pure cellulosic materials and pretreated samples that were dried by different means.  CrI readings varied greatly depending on different techniques, calculation approaches, and drying conditions, suggesting that CrI was not a key determinant of the enzymatic hydrolysis.  These results suggested that cellulose characterization should be conducted under hydrated condition. We have developed a quantitative substrate accessibility assay using a non-hydrolytic fusion protein (TGC), determining cellulose accessibility to cellulase (CAC) 3.  It was found that COSLIF increased surface area of switchgrass from 1.42 to 16.58 m2/g cellulose. The digestibility and surface accessibility results suggested that COSLIF not only broke the linkage among cellulose, lignin, and hemicellulose but also disrupted highly ordered hydrogen bonds in cellulose fibers.  

[1] Sathitsuksanoh et al. Ind. Eng. Chem. Res. 2009, 48, 6441.
[2] Sathitsuksanoh et al. Biores. Technol. DOI: 10.1016/j.biortech.2009.09.081
[3] Zhu et al. Biotechnol. Bioeng. 2009, 103, 715.



Web Page: filebox.vt.edu/users/ypzhang/research.htm

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