Enzyme from wood-eating gribble could help turn waste into biofuel

BUILDING THE BIOECONOMY

• Robust enzyme discovery that could help lead to sustainable biofuels
• Enzyme to create liquid fuel from wood could be produced in the same way that enzymes for biological washing detergents are made
• First 3D image of aquatic animal enzyme provides previously undiscovered picture of how it works

Limnoria - the wood-eating gribble. We are grateful to Dr Alex Ball for permission to use the confocal microscopy facilities at The Natural History Museum for this image. Image: Laura Michie, University of Portsmouth.

Scientists have discovered a new enzyme that could prove an important step in the quest to turn waste (such as paper, scrap wood and straw) into liquid fuel. To do this they turned to the destructive power of tiny marine wood-borers called 'gribble', which have been known to destroy seaside piers.

Using advanced biochemical analysis and X-ray imaging techniques, researchers from the University of York, University of Portsmouth and the National Renewable Energy Laboratory in the USA have determined the structure and function of a key enzyme used by gribble to break down wood. The findings, published in PNAS, will help the researchers to reproduce the enzymes effects on an industrial scale in a bid to create sustainable liquid biofuels.

To create liquid fuel from woody biomass, such as wood and straw, the polysaccharides (sugar polymers) that make up the bulk of these materials have to be broken down into simple sugars. These are then fermented to produce liquid biofuels. This is a difficult process and making biofuels in this way is currently too expensive.

To find more effective and cheaper ways of converting wood to liquid fuel, scientists are studying organisms that can break down wood in hope of developing industrial processes to do the same.

The 3D X-ray structure allows scientists to see inside the enzyme and reveals how it binds and digests cellulose chains. Image: John McGeehan, University of Portsmouth.

Gribble are of interest as they are voracious consumers of wood and have all the enzymes needed for its digestion. The enzymes attach to a long chain of complex sugars and chop off small soluble molecules that can be easily digested or fermented. The researchers identified a cellulase (an enzyme that converts cellulose into glucose) from gribble that has some unusual properties and used the latest imaging technology to understand more about it.

The research team leader, Professor Simon McQueen-Mason, from the Centre for Novel Agricultural Products at the University of York, explains:"Enzymes are proteins that serve as catalysts, in this case one that degrades cellulose. Their function is determined by their three-dimensional shape, but these are tiny entities that cannot be seen with high power microscopes. Instead, we make crystals of the proteins, where millions of copies of the protein are arrayed in the same orientation."

Dr John McGeehan, a structural biologist from the University of Portsmouth team, said: "Once we succeeded in the tricky task of making crystals of the enzyme, we transported them to the Diamond Light Source, the UK's national synchrotron science facility. Rather than magnify the enzyme with a lens as in a standard microscope, we fired an intense beam of X-rays at the crystals to generate a series of images that can be transformed into a 3D model. The Diamond synchrotron produced such good data that we could visualise the position of every single atom in the enzyme. Our US colleagues then used powerful supercomputers, called Kraken and Red Mesa, to model the enzyme in action. Together these results help to reveal how the cellulose chains are digested into glucose."

For further details log on website:

http://www.bbsrc.ac.uk/news/industrial-biotechnology/2013/130603-pr-enzyme-could-turn-waste-into-biofuel/