University of Tennessee and ORNL researchers make lignin extraction progress

In Tennessee, researchers from the University of Tennessee, Knoxville and Oak Ridge National Laboratory used three pretreatment solvents to partially deconstruct and break away plant lignin from other cell wall components so the lignin modules can be extracted. The composition of the extracted lignin (and therefore its potential value) from wild type and genetic variants of switchgrass by each of the solvent conditions is reflected by its measurable molecular mass and remaining chemical bonds. Based on several types of analytical data, the researchers observed differences among the lignin extracts, indicating that various specific types of bioproducts can be generated from the lignin extract from each set of solvent and conditions. The molecular interactions among the solvents, cellulose, and lignin are key to the process. Characterizing those interactions for the set of pretreatment solvents was therefore another research goal. The researchers used computer simulations based on the analytical data to provide insight into the number of molecular interactions between the lignin and solvent molecules. The findings indicate that the ability to form those interactions is important for enabling lignin depolymerization.

The study showed that each of the three solvents and the switchgrass genetic variations are effective in generating lignin extracts of differing forms, suited for distinct uses. For example, the tetrahydrofuran pretreated lignin should be suitable for further depolymerization into monoaromatic compounds. The information from this study can aid in the selection of pretreatment based on the type of precursor modules needed for a particular use.