Neutron Scattering and Supercomputing Gives Closer Look at Lignin and Its Removal from Biomass During Biofuel Processing

Lignin is the tough material component in lignocellulosic biomass which must be removed by pretreatment in order for the biomass to be processed into biofuel-ethanol. Breaking this so-called "lignin barrier" or "biomass recalcitrance" (i.e. "resistance to invasive change") is an important step toward more cost-effective bioethanol production from lignocellulosic biomass. Although many pretreatment methods have been tried in attempt to remove lignin from plant biomass, these have been tried on a partly empirical basis, because the chemical structure of lignin is not yet completely understood. Understanding these chemical mysteries of the lignin molecule can open new developments for more effective pretreatment methods of delignification.

A recent study by researchers from the Department of Energy's Oak Ridge National Laboratory (ORNL, United States) has provided a closer look into the molecule that complicates the production of next-generation biofuels. In their study, they used a combination of neutron scattering experiments and large-scale simulations using the ORNL's Jaguar supercomputer, which is the first of its kind, to reveal the surface structure of lignin down to one angstrom, or ten billionth of a meter.

They found that lignin forms aggregates in vivo and has a highly folded surface. These observations are said to pose a barrier  to cellulosic ethanol production. The lignin aggregates and their highly folded surfaces can bind to the (saccharifying) enzymes and reduce the efficiency of the conversion. (Saccharifying enzymes convert the carbohydrate fraction of pretreated biomass into ethanol-fermentable sugars). The surface of the pretreated softwood lignin is characterized by a highly folded surface. The highly folded nature of the lignin molecule is reported to slow down enzymatic activity.

The full report of the study are published in the journal, Physical Review E (URL above). .