The Department of Energy’s Oak Ridge National Laboratory (ORNL) with a “first of its kind” combination of experiment and simulation is providing a closeup look at the lignin molecule that bedevils making next-generation biofuels.

Lignin is a major component of plant cell walls.  During processing it aggregates or clumps up, which cause problems during the production of biofuels.  As cellulosic ethanol could be the leading biofuel right now it is of particular interest to that industry.

Until now the exact shape and structure of the aggregates or clumps 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 have been published in Physical Review E.

Smith, who directs ORNL’s Center for Molecular Biophysics and holds a Governor’s Chair at University of Tennessee said, “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.”

A Lignin Clump. Image Credit: ORNL. Click image for the largest view.

Lignin’s clumps are now thought to inhibit the conversion of biofuel feedstocks – for example, switchgrass – 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.

And yet lignin’s highly folded surface creates more opportunities to capture the passing enzymes than a smooth surface would. An improved understanding of the lignin clumped aggregates will aid scientists in efforts to design a more effective pretreatment process, which in turn could lower the cost of biofuels.

ORNL team member Loukas Petridis explains further, “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.”

The research is welcome; having a solid visualization offers a better base for intuition and innovation.  As the team at ORNL observed, the folds explain the problem and show where an opportunity might be exploited.

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. “This work illustrates how state-of-the-art neutron scattering and high-performance supercomputing can be integrated to reveal structures of importance to the energy biosciences,” Smith said.

ORNL team members include Sai Venkatesh Pingali, Volker Urban, William Heller, Hugh O’Neill with Marcus Foston and Arthur Ragauskas from Georgia Institute of Technology who with Petridis and Smith make the full squad.

Lignin is a nemesis for further growth in substituting fossil fuel with biomass particularly in liquid transport fuels.  Corn has gotten supplies past 10%, but to crack the market very deeply is going to require that the lignin problem get solved or better still, exploited.

The project is funded by tax dollars flowed through DOE’s Office of Science and used the resources of the Leadership Computing Facility at ORNL under a DOE INCITE award.

Now researchers can see what they’re up against – and that’s a major improvement from the status quo.


3 Comments so far

  1. SlakedMercury on June 17, 2011 1:25 AM

    Great progress. Lignin is the structure of wood that braces up the cellulose bundles. Same in any plant really. I think that it has a structure such that vanilla can be made from it. Trying to remember.

    Anyway, it is a problem in the paper industry too. There are natural enzymes that lead to its consumption by fungi call lignase or close to it. Need a cross between a termite gut bacteria and a yeast so old wood can be converted to vodka.

  2. JP Straley on June 17, 2011 12:21 PM

    Only fungi naturally degrade lignin, and they don’t do it enzymatically. They promote Fe, trade an electron and make an OH-dot radical with close to 4 volts potential (forgive me a little accuracy here, I’m writing from memory).

    This is kind of like working on fiberglass with an acetylene torch!

    In practical terms, if you want to see an old tree stump disappear faster, sprinkle w azeala “food”, as it has chelated iron.

  3. Craig Binns on June 18, 2011 3:04 AM


    The idea of vodka made by fermenting lignin in bacteria-filled termites’ guts isn’t very appetising.

    I’m happy to be able to report that’s not how they make whisky here in Scotland – although the taste of some of the cheaper blends sometimes makes me wonder how the hell they ARE made!

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