Improving Access to Cellulose in Biomass for Biofuel Production

The Science

The conversion of cellulosic biomass to fermentable sugars usually requires costly, time-consuming pretreatment to increase the material’s porosity, decrease its crystallinity, and reduce the amount of structural lignin in the cell wall. Researchers used small-angle neutron scattering at the High-Flux Isotope Reactor to probe the morphological changes of switchgrass cell walls during dilute acid pretreatment, elucidating the interplay of different biomolecular components in the breakdown process. esults demonstrate that dilute acid pretreatment increases the cross-sectional radius of the crystalline cellulose fibril. This change is accompanied by removal of hemicellulose and the formation of Rg ∼ 135 Å lignin aggregates. The structural signature of smooth cell wall surfaces is observed at length scales larger than 1000 Å, and it remains remarkably invariable during pretreatment. The results are important for the development of efficient strategies to convert biomass to biofuel.


Of the many types of plants that have been examined as potential feedstocks for production of ethanol and other fuels, herbaceous crops, particularly grasses, offer a number of advantages. These include fast growth, established agricultural cultivation, and potential for dual-purpose production, providing both grain for food and straw (stalks) for biofuel conversion. Switchgrass (Panicum virgatum), a native North American prairie grass, is being developed as the main herbaceous crop for biofuel production. All lignocellulosic biomass is largely composed of three component biopolymers: cellulose, a linear polymer of β-1,4-linked glucose chains assembled into partially crystalline fibers; hemicellulose, a heterogeneous branched polymer of pentose and hexose sugars; and lignin, which is composed of extensively cross-linked methoxy-substituted phenyl propane units. Cellulose, which forms the main structural component of the plant cell walls, is an attractive source of glucose for fermentative ethanol production, but must be first depolymerized by enzymatic or chemical hydrolysis. In lignocellulosic biomass, enzymatic access to the cellulose fibers is impeded by hemicellulose and lignin layers. As a result, efficient production of fermentable sugars from lignocellulosic biomass requires deconstruction of the plant cell walls by mechanical and chemical pretreatment.


Pingali, S. V., V. S. Urban, W. T. Heller, J. McGaughey, H. O’Neill, M. Foston, D. A. Myles, A. Ragauskas, and B. R. Evans. 2010. “Breakdown of Cell Wall Nanostructure in Dilute Acid Pretreated Biomass,” Biomacromolecules 11, 2329–35. DOI:10.1021/bm100455h.