ORNL X-ray and neutron-scattering research unlocks sectrets of cellulosic biofuels

June 28, 2017 |

In Tennessee, researchers from the Department of Energy’s Oak Ridge National Laboratory and North Carolina State University used a a combination of X-ray and neutron scattering to revealed new insights into how a highly efficient industrial enzyme is used to break down cellulose. Their results are published in the journal Angewandte ChemieInternational Edition.

Producing biofuels like ethanol from plant materials requires various enzymes to break down the cellulosic fibers.  Knowing how oxygen molecules (red) bind to catalytic elements (illustrated by a single copper ion) will guide researchers in developing more efficient, cost-effective biofuel production methods.

Scientists using neutron scattering have identified the specifics of an enzyme-catalyzed reaction that could significantly reduce the total amount of enzymes used, improving production processes and lowering costs.

Part of a larger family known as lytic polysaccharide monooxygenases, or LPMOs, these oxygen-dependent enzymes act in tandem with hydrolytic enzymes—which chemically break down large complex molecules with water—by oxidizing and breaking the bonds that hold cellulose chains together. The combined enzymes can digest biomass more quickly than currently used enzymes and speed up the biofuel production process.

“These enzymes are already used in industrial applications, but they’re not well understood,” said lead author Brad O’Dell, a graduate student from NC State working in the Biology and Soft Matter Division of ORNL’s Neutron Sciences Directorate. “Understanding each step in the LPMO mechanism of action will help industry use these enzymes to their full potential and, as a result, make final products cheaper.”

In an LPMO enzyme, oxygen and cellulose arrange themselves through a sequence of steps before the biomass deconstruction reaction occurs. Sort of like “on your mark, get set, go,” says O’Dell. “This is a big step forward in unraveling how LPMO’s initiate the breakdown of carbohydrates,”

“Because neutrons allow us to see hydrogen atoms inside the enzyme, we gained essential information in deciphering the protein chemistry. Without that data, the role of histidine 157 would have remained unclear,” said coauthor Flora Meilleur, ORNL instrument scientist and an associate professor at NC State. “Neutrons were instrumental in determining how histidine 157 stabilizes oxygen to initiate the first step of the LPMO reaction mechanism.”

Category: Fuels

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