Posted on 3 June 2013
To do this they turned to the destructive power of tiny wood-boring marine isopod called ‘gribble’, which historically attacked the timber hulls of seafarers’ ships, and continue to wreak damage on wooden piers and docks in coastal communities.
Using advanced biochemical analysis and X-ray imaging techniques, scientists from the Centre for Novel Agricultural Products (CNAP) in the Department of Biology at York, the 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 digest wood. This will help the researchers to reproduce its effects on an industrial scale in a bid to create sustainable liquid biofuels. The research is published in the Proceedings of the National Academy of Sciences USA.
To create liquid fuel from woody biomass, such as wood and straw, the polysaccharides (sugar polymers) that make up the bulk of these materials must be broken down into simple sugars. These are then fermented to produce liquid biofuels. This is a difficult and expensive process.
To find more effective ways of converting wood to liquid fuel, scientists are studying organisms that have evolved to live on a diet of woody matter as these could provide a starting point for developing industrial enzymes to do the same.
Gribble 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 then 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.
Professor McQueen-Mason, of CNAP, said: “Enzymes are proteins that serve as catalysts, in this case one that degrades cellulose. Their function is determined by their three-dimensional shape and by studying the structure of the enzyme we have found a number of unusual features that could be of benefit to the biofuels industry."
While similar cellulase have been characterised from wood-degrading fungi, the enzyme from gribble shows some important differences. In particular, the gribble cellulase is extremely resistant to aggressive chemical environments and can work in conditions seven times saltier than sea water. Being robust to difficult environments means that the enzymes can last much longer when working under industrial conditions and so less enzyme will be needed. Understanding the structural basis for this robustness will help the researchers to design more robust enzymes for industrial applications.
The robust nature of the enzymes makes it compatible for use in conjunction with sea water, which would lower the costs of processing.
Professor McQueen-Mason explained: “This is the first functionally characterized animal enzyme of this type and provides us with a previously undiscovered picture of how they work.
“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.”
The ultimate aim is to reproduce the effect of this enzyme on an industrial scale. Rather than trying to get the cellulase from gribble, the team have transferred the genetic blueprint of this enzyme to an industrial microbe that can produce it in large quantities, in the same way that enzymes for biological washing detergents are made. By doing this they hope to cut the costs of turning woody materials into biofuels.
Professor Bruce 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.”
The work is part of the BBSRC Sustainable Bioenergy Centre (BSBEC), a £24m investment that brings together six world-class research programmes to develop the UK's bioenergy research capacity. Visits between the research teams were supported by a BBSRC USA Partnering Award.
Douglas Kell, BBSRC’s Chief Executive, said: “This is an exciting step in realising the potential of these important enzymes. If we can harness them effectively, waste materials could be used to make sustainable fuels. It’s a double bonus; avoiding competition with land for food production as well as utilising unused materials from timber and agricultural industries.”
The imaging was conducted at Diamond Light Source, the UK's national synchrotron science facility.