Probing Morphological Changes in Pretreated Lignocellulosic Biomass by Small-Angle Neutron Scattering

Researchers from the Oak Ridge National Laboratory of the United States Department of Energy (US-DOE) and the Georgia Institute of Technology (United States), report the use of "small-angle neutron scattering" to probe the structural impact of acid pretreatment on the lignocellulosic structure of switchgrass. This technique is reported to provide new insights into morphological changes of pretreated biomass, in the search for cost-effective pretreatment processes for cellulose-ethanol production. (Pretreatment is the first step in the production of cellulose-ethanol production from lignocellulosic biomass; its purpose is to release the cellulose and hemicelluloses molecules from its tight lignin wrapping, by chemical (acid, alkali) and/or thermal methods). The researchers used the observation technique on acid-pretreated switchgrass. They found that the diameter of the crystalline portion of a cellulose fibril increases from about 21 angstroms before treatment to 42 angstroms after treatment. They also found that lignin concurrently undergoes "a redistribution process and forms aggregates, or droplets, which are 300 angstroms to 400 angstroms in size". The results suggest that hot dilute sulfuric acid pretreatment effectively decreases "biomass recalcitrance" by making cellulose more accessible to enzymatic attack, through lignin redistribution and hemicellulose removal; however, its efficiency may be limited because of possible "re-annealing" of the cellulose molecules (as indicated by the apparent increase in cellulose fibril diameter). The full results of the study is published in the 2010 September 13 issue of the journal, Biomacromolecules. According to researcher and co-author, Volker Urban, "Ultimately, the ability to extract meaningful structural information from different native and pretreated biomass samples will enable evaluation of various pretreatment protocols for cost-effective biofuels production".

Related information: BioMacromolecules journal website http://pubs.acs.org/toc/bomaf6/current