Oak Ridge team reveals surface structure of lignin; highly folded surface impedes enzymatic hydrolysis
A first of its kind combination of experiment and simulation at the US Department of Energy’s Oak Ridge National Laboratory (ORNL) is providing a close-up look at the lignin molecule that complicates next-generation biofuels. Lignin, a major component of plant cell walls, aggregates to form clumps, which cause problems during the production of cellulosic ethanol. The exact shape and structure of the aggregates, however, have remained largely unknown.
A team led by ORNL’s Jeremy Smith revealed the surface structure of lignin aggregates down to 1 angstrom—the equivalent of a 10 billionth of a meter or smaller than the width of a carbon atom. The team’s findings were published in the journal Physical Review E.
We’ve combined neutron scattering experiments with large-scale simulations on ORNL’s main supercomputer to reveal that pretreated softwood lignin aggregates are characterized by a highly folded surface.—Jeremy Smith
Lignin clumps can inhibit the conversion of biofuel feedstocks into ethanol, a renewable substitute for gasoline. When enzymes are used to release plant sugars necessary for ethanol production, the lignin aggregates bind to the enzymes and reduce the efficiency of the conversion.
Lignin’s highly folded surface creates more opportunities to capture the passing enzymes than a smooth surface would. An improved understanding of the lignin aggregates will aid scientists in efforts to design a more effective pretreatment process, which in turn could lower the cost of biofuels.
Nature has evolved a very sophisticated mechanism to protect plants against enzymatic attack. We’re trying to understand the physical basis of biomass recalcitrance—resistance of the plants to enzymatic degradation.—ORNL team member Loukas Petridis
The complementary techniques of simulation on ORNL’s Jaguar supercomputer and neutron scattering at the lab’s High Flux Isotope Reactor enabled Smith’s team to resolve lignin’s structure at scales ranging from 1 to 1,000 angstroms. Smith’s project is the first to combine the two methods in biofuel research.
The research was supported by DOE’s Office of Science and used the resources of the Leadership Computing Facility at ORNL under a DOE INCITE award. Team members include ORNL’s Sai Venkatesh Pingali, Volker Urban, William Heller, Hugh O'Neill and Marcus Foston and Arthur Ragauskas from Georgia Institute of Technology.
Loukas Petridis, Sai Venkatesh Pingali, Volker Urban, William T. Heller, Hugh M. O’Neil, Marcus Foston, Arthur Ragauskas, and Jeremy C. Smith (2011) Self-similar multiscale structure of lignin revealed by neutron scattering and molecular dynamics simulation. Phys. Rev. E 83, 061911 doi: 10.1103/PhysRevE.83.061911