Understanding the impact of ionic liquid pretreatment on eucalyptus

Çetinkol, Özgül Persil
Dibble, Dean C
Cheng, Gang
Kent, Michael S
Knierim, Bernhard
Auer, Manfred
Wemmer, David E
Pelton, Jeffrey G
Melnichenko, Yuri B
Ralph, John
Simmons, Blake A
Holmes, Bradley M

¹Joint BioEnergy Institute, Deconstruction Division, Emeryville, CA, USA
²Lawrence Berkeley National Laboratory, Physical Biosciences Division, Berkeley, CA, USA
³Sandia National Laboratories, Livermore, CA, USA, and Albuquerque, NM, USA. E-mail: [email protected]
⁴Joint BioEnergy Institute, Technology Division, Emeryville, CA, USA
⁵Department of Chemistry and California Institute for Quantitative Biosciences, University of California, Berkeley, CA, USA
⁶Oak Ridge National Laboratory, Spallation Neutron Source, Knoxville, TN, USA
⁷DOE Great Lakes BioEnergy Research Center, and Departments of Biochemistry and Biological Systems Engineering, University of Wisconsin-Madison, Madison, WI, USA

^† Author for correspondence

Biofuels 1(1):p 33-46, January 2010. | DOI: 10.4155/bfs.09.5

Background:

The development of cost-competitive biofuels necessitates the realization of advanced biomass pretreatment technologies. Ionic liquids provide a basis for one of the most promising pretreatment technologies and are known to allow effective processing of cellulose and some biomass species.

Results & discussion:

Here, we demonstrate that the ionic liquid 1-ethyl-3-methyl imidazolium acetate, [C2mim][OAc], induces structural changes at the molecular level in the cell wall of Eucalyptus globulus. Deacetylation of xylan, acetylation of the lignin units, selective removal of guaiacyl units (increasing the syringyl:guaiacyl ratio) and decreased β-ether content were the most prominent changes observed. Scanning electron microscopy images of the plant cell wall sections reveal extensive swelling during [C2mim][OAc] pretreatment. X-ray diffraction measurements indicate a change in cellulose crystal structure from cellulose I to cellulose II after [C2mim][OAc] pretreatment. Enzymatic saccharification of the pretreated material produced increased sugar yields and improved hydrolysis kinetics after [C2mim][OAc] pretreatment.

Conclusion:

These results provide new insight into the mechanism of ionic liquid pretreatment and reaffirm that this approach may be promising for the production of cellulosic biofuels from woody biomass.