LESS CHEWING THE CUD, MORE GREENING THE FUEL
Making grasses more digestible promises improved feed for ruminants and better biomass for biofuel production, with economic and environmental benefits for both.
Plant biomass contains considerable calorific value but most of it makes up robust cell walls, an unappetising evolutionary advantage that helped grasses to survive foragers and prosper for more than 60 million years.
The trouble is that this robustness still makes them less digestible in the rumen of cows and sheep and difficult to process in bioenergy refineries for ethanol fuel.
But now a multinational team of researchers, from the UK, Brazil and the US, has pinpointed a gene involved in the stiffening of cell walls whose suppression increased the release of sugars by up to 60%. Their findings are reported today in New Phytologist.
“The impact is potentially global as every country uses grass crops to feed animals and several biofuel plants around the world use this feedstock,” says Rowan Mitchell, a plant biologist at Rothamsted Research and the team’s co-leader.
“In Brazil alone, the potential markets for this technology were valued last year at R$1300M ($400M) for biofuels and R$61M for forage cattle,” says Hugo Molinari, Principal Investigator of the Laboratory of Genetics and Biotechnology at Embrapa Agroenergy, part of the Brazilian Agricultural Research Corporation (Embrapa) and the team’s other co-leader.
Jalles Machado refinery in Brazil produces sugar cane, ethanol and electricity. Credit: Daniela Collares/Embrapa Agroenergia
Billions of tonnes of biomass from grass crops are produced every year, notes Mitchell, and a key trait is its digestibility, which determines how economic it is to produce biofuels and how nutritious it is for animals. Increased cell wall stiffening, or feruloylation, reduces digestibility.
“We identified grass-specific genes as candidates for controlling cell wall feruloylation 10 years ago, but it has proved very difficult to demonstrate this role although many labs have tried,” says Mitchell. “We now provide the first strong evidence for one of these genes.”
In the team’s genetically modified plants, a transgene suppresses the endogenous gene responsible for feruloylation to around 20% of its normal activity. In this way, the biomass produced is less feruloylated than it would otherwise be in an unmodified plant.
“The suppression has no obvious effect on the plant’s biomass production or on the appearance of the transgenic plants with lower feruloylation,” notes Mitchell. “Scientifically, we now want to find out how the gene mediates feruloylation. In that way, we can see if we can make the process even more efficient.”
The findings are undoubtedly a boon in Brazil, where a burgeoning bioenergy industry produces ethanol from the non-food leftovers of other grass crops, such as maize stover and sugarcane residues, and from sugar cane grown as a dedicated energy crop. Increased efficiency of bioethanol production will help it to replace fossil fuel and reduce greenhouse gas emissions.
“Economically and environmentally, our livestock industry will benefit from more efficient foraging and our biofuels industry will benefit from biomass that needs fewer artificial enzymes to break it down during the hydrolysis process,” notes Molinari.
More digestible grasses could improve feed for livestock, for the economy and for the environment.
For John Ralph, co-author and field pioneer, the discovery has been hard won and is long overdue. “Various research groups ‘had the feruloylation protein/gene imminently’, and that was some 20 years ago,” notes the Professor of Biochemistry at the University of Wisconsin-Madison and at the US Department of Energy’s Great Lakes Bioenergy Research Center.
“Our group has been interested, since the early 1990s, in ferulate cross-linking in plant cell walls and developed the NMR methods that were useful in the characterisation here,” notes Ralph. “This has been a tough one to discover.”
De Souza et al., 2018: Suppression of a single BAHD gene in Setaria viridis causes large, stable decreases in cell wall feruloylation and increases biomass digestibility. New Phytologist
Mitchell et al., 2007. A novel bioinformatics approach identifies candidate genes for the synthesis and feruloylation of arabinoxylan. Plant Physiology
Embrapa Agroenergy contacts:
Hugo Molinari, Director of Research
Laboratory of Genetics and Biotechnology
Tel: +55 (61) 3448-2307
Daniela Collares, Head of Communications
Tel: +55 (61) 3448-1581
The Brazilian Agricultural Research Corporation (Empresa Brasileira de Pesquisa Agropecuária, or Embrapa) was founded on 26 April, 1973 and is linked to the Ministry of Agriculture, Livestock and Supply (Ministério da Agricultura, Pecuária e Abastecimento, or Mapa). Embrapa has 46 research centres (technical, product, eco-regional and service) and 16 business offices all over the country. Since its formation, Embrapa has been tasked with developing, in partnership with the National System for Agricultural Research (Sistema Nacional de Pesquisa Agropecuária, or SNPA), a genuinely Brazilian tropical agriculture and livestock model that overcomes barriers limiting production of foodstuffs, fibres and energy in our country. This effort has helped to transform Brazil. The national agricultural sector is today one of the most efficient and sustainable on the planet. A wide area of land degraded in the Brazilian Savanna has been made productive; a region that is now responsible for about 50% of all grain production. Beef and pork production has increased fourfold, and chicken production by 22 times. These are some of the achievements that have brought our country from a position of being an importer of basic foodstuffs to one of the largest producers and exporters worldwide.
For more information on Embrapa, visit https://www.embrapa.br/
For more information on Embrapa Agroenergia, visit https://www.embrapa.br/agroenergia; Twitter @cnpae
University of Wisconsin-Madison contact:
John Ralph, Professor of Biochemistry
Tel: +1 (608) 890-2429
About University of Wisconsin-Madison/DOE Great Lakes Bioenergy Research Center
The University of Wisconsin is a large top-10 land-grant university in the US. Its Great Lakes Bioenergy
Research Center (GLBRC), established in 2007 by the Biological and Environmental Research Program in the US Department of Energy (DOE)’s Office of Science, is conducting transformational research into pro-ducing sustainable biofuels and bioproducts from dedicated energy crops grown on marginal lands.
For more information, https://www.wisc.edu/
For more information on GLBRC, visit www.glbrc.org; Twitter @glbioenergy
About Rothamsted Research
Rothamsted Research is the longest-running agricultural research institute in the world. We work from gene to field with a proud history of ground-breaking discoveries, from crop treatment to crop protection, from statistical interpretation to soils management. Our founders, in 1843, were the pioneers of modern agriculture, and we are known for our imaginative science and our collaborative influence on fresh thinking and farming practices.
Through independent science and innovation, we make significant contributions to improving agri-food systems in the UK and internationally. In terms of the institute’s economic contribution, the cumulative impact of our work in the UK was calculated to exceed £3000 million a year in 20151. Our strength lies in our systems approach, which combines science and strategic research, interdisciplinary teams and partnerships.
Rothamsted is also home to three unique resources. These National Capabilities are open to researchers from all over the world: The Long-Term Experiments, Rothamsted Insect Survey and the North Wyke Farm Platform.
We are strategically funded by the Biotechnology and Biological Sciences Research Council (BBSRC), with additional support from other national and international funding streams, and from industry. We are also supported by the Lawes Agricultural Trust (LAT).
For more information, visit https://www.rothamsted.ac.uk/; Twitter @Rothamsted
1Rothamsted Research and the Value of Excellence: A synthesis of the available evidence, by Séan Rickard (Oct 2015)
The Biotechnology and Biological Sciences Research Council is part of UK Research and Innovation, a non-departmental public body funded by a grant-in-aid from the UK government.
BBSRC invests in world-class bioscience research and training on behalf of the UK public. Our aim is to further scientific knowledge, to promote economic growth, wealth and job creation and to improve quality of life in the UK and beyond.
Funded by government, BBSRC invested £469 million in world-class bioscience in 2016-17. We support research and training in universities and strategically funded institutes. BBSRC research and the people we fund are helping society to meet major challenges, including food security, green energy and healthier, longer lives. Our investments underpin important UK economic sectors, such as farming, food, industrial biotechnology and pharmaceuticals.
More information about BBSRC, our science and our impact.
More information about BBSRC strategically funded institutes
The Lawes Agricultural Trust, established in 1889 by Sir John Bennet Lawes, supports Rothamsted Research’s national and international agricultural science through the provision of land, facilities and funding. LAT, a charitable trust, owns the estates at Harpenden and Broom's Barn, including many of the buildings used by Rothamsted Research. LAT provides an annual research grant to the Director, accommodation for nearly 200 people, and support for fellowships for young scientists from developing countries. LAT also makes capital grants to help modernise facilities at Rothamsted, or invests in new buildings.