Location: Wheat, Sorghum and Forage ResearchTitle: Visualization of Biomass Solubilization and Cellulose Regeneration during Ionic Liquid Pretreatment of Switchgrass Author
Submitted to: Biotechnology and Bioengineering
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/20/2009
Publication Date: 7/13/2009
Publication URL: http://hdl.handle.net/10113/44132
Citation: Singh, S., Simmons, B., Vogel, K.P. 2009. Visualization of Biomass Solubilization and Cellulose Regeneration during Ionic Liquid Pretreatment of Switchgrass. Biotechnology and Bioengineering 104:68-75. DOI 10.1002/bit.22386 Interpretive Summary: Biomass from bioenergy crops such as switchgrass can be converted to liquid fuels such as ethanol by converting the cell wall cellulose and hemicellulose via enzymes to fermentable sugars. Because cell wall cellulose and hemicellulose are tightly bound to lignin which impedes the enzymatic breakdown of cell walls to simple sugars, pre-treatment methods are being developed to break down the tight bonding between lignin and cell wall celluloses. An ionic liquid was evaluated for its effectiveness in disrupting the bonds between lignin and cellulose fibrils of switchgrass biomass. In comparison to untreated biomass, ionic liquid pretreated biomass produced cellulose that was efficiently hydrolyzed with cellulases with high sugar yields. Laser confocal fluorescence microscopy analysis of the treated biomass demonstrated that the ionic liquid treatment resulted in disruption and solubilization of the plant cell wall at mild temperatures. The results indicate that ionic liquids have potential for pre-treating biomass for conversion to ethanol.
Technical Abstract: Auto-fluorescent mapping of plant cell walls was used to visualize cellulose and lignin in pristine switchgrass (Panicum virgatum) stems to determine the mechanisms of biomass dissolution during ionic liquid pretreatment. The addition of ground switchgrass to the ionic liquid 1-n-ethyl-3-methylimidazolium acetate resulted in the disruption and solubilization of the plant cell wall at mild temperatures. Swelling of the plant cell wall, attributed to disruption of inter- and intra-molecular hydrogen bonding between cellulose fibrils and lignin, followed by complete dissolution of biomass, was observed without using imaging techniques that require staining, embedding and processing of biomass. Subsequent cellulose regeneration via the addition of an anti-solvent, such as water, was observed in situ and provided direct evidence of significant rejection of lignin. This was confirmed by chemical analysis of the regenerated cellulose. In comparison to untreated biomass, ionic liquid pretreated biomass produces cellulose that is efficiently hydrolyzed with cellulases with high sugar yields.