Plant enzyme discovery could improve viability of biofuels

Researchers funded by the Biotechnology and Biological Sciences Research Council have discovered key plant enzymes that normally make the energy stored in wood, straw and other non-edible parts of plants difficult to extract.

The findings could be used to improve the viability of sustainable biofuels that do not adversely affect the food chain.

The team, based at Cambridge University and now part of the BBSRC Sustainable Bioenergy Centre (BSBEC), has identified and studied the genes for two enzymes that toughen wood, straw and stalks and so make it difficult to extract sugars to make bioethanol or other plant-derived products.

According to a statement, this knowledge can now be used in crop breeding programmes to make non-edible plant material that requires less processing, energy and chemicals for conversion to biofuels or other renewable products and that has a lower overall impact on atmospheric carbon.

The research is also said to increase the economic viability of producing sustainable biofuels from the inedible by-products of crops through the increased understanding of plant structures.

Lead researcher Prof Paul Dupree said: ‘There is a lot of energy stored in wood and straw in the form of a substance called lignocellulose. We wanted to find ways of making it easier to get at this energy and extract it in the form of sugars that can be fermented to produce bioethanol and other products.’

Lignocellulose gives plants strength and rigidity and one of its main components is xylan. Xylan in wood and straw represents about a third of the sugars that could potentially be used to make bioethanol, but it is locked away. Releasing the energy from lignocellulose is an important challenge to tackle as it will allow the production of fuels from plants in a sustainable way that does not affect the food chain.

‘What we didn’t want to do was end up with floppy plants that can’t grow properly, so it was important to find a way of making xylan easier to break down without having any major effects,’ said Dupree.

The team studied Arabidopsis plants (which are easy to study in the laboratory) that lack two of the enzymes that build the xylan part of lignocellulose in plants. The researchers found that although the stems of the plants are slightly weaker than normal, they grow normally and reach a normal size.

They also tested how easy it would be to extract sugars from these plants and discovered that it takes less effort to convert all the xylan into sugar.

Dupree said: ‘The next stage will be to work with our colleagues who are developing new varieties of bioenergy crops such as willow and miscanthus grass to see if we can breed plants with these properties and to use our discovery to develop more sustainable processes for generating fuels from crop residues. We expect to work closely with industrial collaborators to see how we can quickly transfer this research into real applications for transport fuels.

’Working in consort with the other five hubs of the BBSRC Sustainable Bioenergy Centre, this research is aimed at improving our ability to release energy stored in plants in a form that is usable in normal everyday applications.’

The findings have been published in Proceedings of the National Academy of Sciences.

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