Biofuels From Waste — Enzyme From Tiny Marine Wood-Borers May Provide Cost-Effective Means To Produce Biofuel

A new enzyme — capable of aiding in the cost-effective conversion of woody-waste into liquid fuel — was recently discovered during research on the tiny marine wood-borers known as ‘gribble’. The extremely small animals are well known for their ability to completely destroy seaside piers, primarily as a result of the powerful enzymes that they use.

Image Credit: Laura Michie, Portsmouth University, with assistance from Alex Ball from the Natural History Museum

By utilizing advanced biochemical analysis and X-ray techniques, the researchers — from the University of York, University of Portsmouth, and the National Renewable Energy Laboratory — were able to ascertain the exact structure and function of the primary enzyme that the gribble use to break down wood. The researchers think that this discovery — if utilized on the industrial scale — will allow for a more cost-effective means of converting waste into biofuel.

In order to produce liquid biofuel from woody biomass (paper, wood scraps, straw, etc), the polysaccharides (sugar polymers) that these materials are primarily composed of needs to be broken down into the simple sugars. These simple sugars can then be fermented and refined — creating liquid biofuels.

The press release continues:

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.

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.

Lead researcher, 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, says: “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.”

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

According to the researchers, all of this new data and knowledge will allow for the creation of robust enzymes which could be used in an industrial setting. Previous research has identified similar cellulases which are used by wood-degrading fungi, but this new enzyme appears to be much more robust than those, capable of withstanding harsh industrial practices. This resiliency means that less enzymes will be needed, helping to further cut down on the costs of biofuel production.

Professor McQueen-Mason explains: “While this enzyme looks superficially similar to equivalent ones from fungi, closer inspection highlights structural differences that give it special features, for example, the enzyme has an extremely acidic surface and we believe that this is one of the features that contributes to its robustness.”

Professor McQueen-Mason added: “The robust nature of the enzymes makes it compatible for use in conjunction with sea water, which would lower the costs of processing. Lowering the cost of enzymes is seen as critical for making biofuels from woody materials cost effective. Its robustness would also give the enzymes a longer working life and allow it to be recovered and re-used during processing.”

The research was just published in PNAS.