Limited availability of fossil fuels stimulates the search for different energy resources. The use of biofuels is one of the alternatives. Sugars derived from the grain of agricultural crops can be used to produce biofuel but these crops occupy fertile soils needed for food and feed production. Fast growing plants such as poplar, eucalyptus, or various grass residues such as corn stover and sugarcane bagasse do not compete and can be a sustainable source for biofuel. An international collaboration of plant scientists from VIB and Ghent University (Belgium), the University of Dundee (UK), The James Hutton Institute (UK) and the University of Wisconsin (USA) identified a new gene in the biosynthetic pathway of lignin, a major component of plant secondary cell walls that limits the conversion of biomass to energy. These findings are published online in this week’s issue of Science Express pave the way for new initiatives supporting a bio-based economy.
“This exciting, fundamental discovery provides an alternative pathway for altering lignin in plants and has the potential to greatly increase the efficiency of energy crop conversion for biofuels," said Sally M. Benson, director of Stanford University's Global Climate and Energy Project. "We have been so pleased to support this team of world leaders in lignin research and to see the highly successful outcome of these projects.”
“This finding was quite unexpected because the lignin pathway has been widely examined and, it had been thought for the past decade or so, completely mapped,” said Professor Claire Halpin, of the University of Dundee. “However, we have now uncovered this enzyme which represents a new step on the pathway and a very important one.
“It looks like it could be very useful in trying to manipulate plant biomass to generate biofuels and other chemicals from non-food crops. Our studies showed that in the plant we studied – Arabidopsis – those with mutated CSE were able to release around 75% more sugars from cellulose without needing harsh chemical treatments. ”
Dr Gordon Simpson, of the University of Dundee and The James Hutton Institute, said, “It has taken an international collaboration that combined expertise in plant genetics, biochemistry and chemical analysis to make sense of this discovery.”
Lignin as a barrier
To understand how plant cells can deliver fuel or plastics, a basic knowledge of a plant’s cell wall is needed. A plant cell wall mainly consists of lignin and sugar molecules such as cellulose. Cellulose can be converted to glucose which can then be used in a classical fermentation process to produce alcohol, similar to beer or wine making. Lignin is a kind of cement that embeds the sugar molecules and thereby gives firmness to plants. Thanks to lignin, even very tall plants can maintain their upright stature. Unfortunately, lignin severely reduces the accessibility of sugar molecules for biofuel production. The lignin cement has to be removed via an energy-consuming and environmentally unfriendly process. Plants with a lower amount of lignin or with lignin that is easier to break down can be a real benefit for biofuel and bioplastics production. The same holds true for the paper industry that uses the cellulose fibres to produce paper.
A new enzyme
For many years researchers have been studying the lignin biosynthetic pathway in plants. Increasing insight into this process can lead to new strategies to improve the accessibility of the cellulose molecules. Using the model plant Arabidopsis thaliana, an international research collaboration between VIB and Ghent University (Belgium), the University of Dundee (UK), the James Hutton Institute (UK) and the University of Wisconsin (USA) has now identified a new enzyme in the lignin biosynthetic pathway. This enzyme, caffeoyl shikimate esterase (CSE), fulfils a central role in lignin biosynthesis. Knocking-out the CSE gene, resulted in 36% less lignin per gram of stem material. Additionally, the remaining lignin had an altered structure. As a result, the direct conversion of cellulose to glucose from un-pretreated plant biomass increased four-fold, from 18% in the control plants to 78% in the cse mutant plants.
These new insights, published this week online in Science Express, can now be used to screen natural populations of energy crops such as poplar, eucalyptus, switchgrass or other grass species for a non-functional CSE gene. Alternatively, the expression of CSE can be genetically engineered in energy crops. A reduced amount of lignin or an adapted lignin structure can contribute to a more efficient conversion of biomass to energy.
This research was co-financed by the multidisciplinary research partnership ‘Biotechnology for a sustainable economy’ of Ghent University, the DOE Great Lakes Bioenergy Research Center and the ‘Global Climate and Energy Project’ (GCEP). Based at Stanford University, the Global Climate and Energy Project is a worldwide collaboration of premier research institutions and private industry that supports research on technologies that significantly reduce emissions of greenhouse gases, while meeting the world’s energy needs.
Note to the editor
EMBARGO – 15 August 2013 – 2 pm US Eastern time
When reporting on this research, please mention all partners involved.
VIB is a non-profit research institute in life sciences. About 1,300 scientists conduct strategic basic research on the molecular mechanisms that are responsible for the functioning of the human body, plants, and microorganisms. Through a close partnership with four Flemish universities - UGent, KU Leuven, University of Antwerp, and Vrije Universiteit Brussel - and a solid funding program, VIB unites the forces of 76 research groups in a single institute. The goal of the research is to extend the boundaries of our knowledge of life. Through its technology transfer activities, VIB translates research results into products for the benefit of consumers and patients and contributes to new economic activity. VIB develops and disseminates a wide range of scientifically substantiated information about all aspects of biotechnology. More information: www.vib.be
After more than twenty years of uninterrupted growth, Ghent University is now one of the most important institutions of higher education and research in the Low Countries. Ghent University yearly attracts over 30,000 students, with a foreign student population of over 2,200 EU and non-EU citizens. Ghent University offers a broad range of study programmes in all academic and scientific branches. With a view to cooperation in research and community service, numerous research groups, centres and institutes have been founded over the years. More info: www.ugent.be
The University of Dundee
The University of Dundee is internationally recognised for its excellence in life sciences and medical research with particular expertise in cancer, diabetes, cardiovascular disease, neuroscience, skin diseases and plant sciences. The University has a top-rated medical school with research expanding from "the cell to the clinic to the community", while the College of Life Sciences is home to some of the world's most cited scientists and more than 800 research staff from 60 different countries. Dundee was voted best in the UK for student experience in the 2012 Times Higher Education Student Experience Survey. See www.dundee.ac.uk for further details.
The James Hutton Institute
The James Hutton Institute is a world-leading scientific organisation encompassing a distinctive range of integrated strengths in land, crop, waters, environmental and socio-economic science. It undertakes research for customers including the Scottish and UK Governments, the EU and other organisations worldwide. The institute has a staff of nearly 600 and 120 PhD students. The Institute organises its research through seven principal themes: Safeguarding Natural Capital, Enhancing Crop Productivity and Utilisation, Delivering Sustainable Production Systems, Controlling Weeds, Pests and Diseases, Managing Catchments and Coasts, Realising Land’s Potential and Nurturing Vibrant and Low Carbon Communities. The James Hutton Institute operates commercial subsidiaries. Macaulay Scientific Consulting (MSC) Ltd is a leading environmental consultancy centre offering unparalleled experience in soil and water consultancy, and land evaluation. Mylnefield Research Services (MRS) Ltd undertakes contract research, especially plant breeding, licenses plant varieties internationally and delivers analytical services. The Institute takes its name from the 18th century Scottish Enlightenment scientist, James Hutton, who is widely regarded as the founder of modern geology and who was also an experimental farmer and agronomist.
University of Wisconsin-Madison
The University of Wisconsin-Madison is a public, land-grant institution located in Madison, Wisconsin. Recognized as one of America’s great universities in both achievement and prestige, UW-Madison offers a complete spectrum of liberal arts studies, professional programs and student activities. The university is the only academic institution to host one of the three U.S. Department of Energy (DOE) Bioenergy Research Centers, which were funded to make transformational breakthroughs that will form the foundation of new cellulosic biofuels technology. The Great Lakes Bioenergy Research Center (GLBRC) is led by UW-Madison with Michigan State University as the major partner. GLBRC’s additional scientific partners include DOE National Laboratories, other universities and a biotechnology company. For more information, please visit http://www.glbrc.org.
16 Aug 2013
New possibilities for efficient biofuel production