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Plants for Food, Energy, Materials, Health and Eco-systems

Studying at Cambridge

 

Lignocellulosic Biomaterials and Bioenergy

The Dupree Lab focuses on utilising parts of food and materials crops that are normally discarded as waste, as well as species that flourish on marginal land with minimal agricultural inputs. Second generation biofuels avoid use of precious food resources, have a greater potential for reducing greenhouse gas emissions, and use plant raw material that is cheap and abundant.

Lignocellulosic Bioenergy

Developing land plant-based fuels that do not compete with food crops

Research carried out in the Dupree Lab

Ethanol produced from plant biomass has the potential to be part of the low carbon solution to replace our fossil liquid transport fuels. Pressures on world agricultural resources, from issues such as climate change and an exploding world population, require creative solutions to produce these biofuels. The Dupree Lab focuses on utilising parts of food and materials crops that are normally discarded as waste, as well as species that flourish on marginal land with minimal agricultural inputs. Second generation biofuels avoid use of precious food resources, have a greater potential for reducing greenhouse gas emissions, and use plant raw material that is cheap and abundant.

Plants store most of the carbon they take from the atmosphere in their cell wall polysaccharides. The plant cell wall is a complex mixture of cellulose, hemicelluloses (including xylan and mannan) and lignin. Current biofuel production focuses on cellulose, with hemicelluloses inefficiently used. Second generation biofuels need to utilise as much of the cell wall as possible, with minimal use of expensive chemical and enzymatic treatment, but much research is needed to make this an industrial reality.

Work in the lab focuses on many aspects of improving plants for biofuel production. These include:

  • Understanding how plants synthesise cell wall polysaccharides
  • Optimising polysaccharide synthesis and structure
  • Characterising cell wall degrading enzymes
  • Developing tools for polysaccharide analysis

 Academics currently involved in the project include:


We are one of the six research hubs in The BBSRC Sustainable Bioenergy Centre. This virtual centre is composed of academic and industrial partners, based at each of the Universities of Cambridge, Dundee, Nottingham and York and Rothamsted Research.

Our contribution is the BSBEC Cell Wall Sugars Programme - developing strategies to improve plants and enzymes for increased sugar release from biomass. The programme aims to better understand how sugars are locked into plant cell walls. By doing this we can select the right plants and the right enzymes to release the maximum amount of sugars for conversion to biofuels.

 

 

Solid state NMR studies of timber

Understanding the molecular architecture of timber using solid state NMR

 

              Solid state NMR

                             

Researchers from Cambridge lab led by Prof Paul Dupree (Department of Biochemistry, University of Cambridge) together with researchers led by his father, Prof Ray Dupree, from University of Warwick are gaining insight into the molecular architecture of wood. Their research uses solid state NMR to analyse the structure of timber. The work was recently published in Nature Communications and Nature Plants and provides novel insights into how components of timber come together to form the strong and resistant material. 

Timber is mainly composed of plant secondary cell walls - an intricate material of polysaccharides and phenolic compounds which surround wood cells. Due to the abundance of trees, plant secondary cell walls are the largest renewable resource of bioenergy on the planet. Sugars extracted from wood can be converted to biofuels. In addition, timber can be a sustainable source of advanced biomaterials such as nanocellulose with applications in food, medicicines and electronics.

Traditionally, wood is studied using biochemical analysis of individual components. Polysaccharides constituting the plant cell walls are isolated and looked at independently of the other components of biomass. This approach allowed characterisation of chemical composition of timber. However, it does not allow for analysis and understanding of the interaction between polysaccharides, or their structure, within an intact piece of wood.

OMT

To gain an understanding of the intact wood structure, researchers working at the University of Cambridge and University of Warwick are developing ways to use solid state Nuclear Magnetic Resonance (NMR). Similarly to magnetic resonance imaging (MRI) used by medical doctors, solid state NMR uses magnetic fields and radio-waves which can be used to decipher the structure of a material. The insights gained with the solid state NMR studies of a model plant Arabidopsis thaliana enabled the Cambridge and Warwick researchers to propose a model of wood molecular architecture.

 

                 cellulose-xylan

Model of cell wall molecular architecture. Xylan (green molecule) can interact with the cellulose microfibril (pink molecule).

 

The key wood components investigated by the group are cellulose and xylan. Cellulose is a crystalline, rod like structure, formed from a linear chain (called a polymer) of glucose and providing mechanical strength to wood. The key discovery from this work came when the group looked at xylan, a polymer of xylose sugars with branches of other sugars. The scientists were surprised to observe that xylan adapts a specific shape within wood. The in-depth analysis of solid state NMR data enabled them to conclude that xylan only binds one, surface of the cellulose crystal that has a suitable shape to stick to the xylan.

In the recent work published in Nature Plants the group has demonstrated that by altering the biosynthesis of xylan its structure can be changed. This led to formation of xylan molecules which are no longer able to interact with cellulose.  “This study is the first demonstration that the structure of xylan in the cell wall affects the xylan-cellulose interaction.” says Oliver Terrett, a PhD student and contributor to the publication, “Rather than being a random mixture of polysaccharides, there are specific interactions in the cell wall. These determine the properties we are interested in, such as strength.”

This opens the way for generation of improved timber, by better wood treatments and perhaps by plant breeding, to suit the needs of both bioenergy and advanced material industries.

Key publications:

Grantham N. et al., An even pattern of xylan substitution is critical for interaction with cellulose in plant cell walls. Nature Plants, 2017, DOI: 10.1038/s41477-017-0030-8

Simmons T. et al., Folding of xylan onto cellulose fibrils in plant cell walls revealed by solid-state NMR. Nature Communications, 2016, 7 (13902); DOI:10.1038/ncomms13902

Dupree R. et al., Probing the Molecular Architecture of Arabidopsis thaliana Secondary Cell Walls Using Two- and Three-Dimensional 13C Solid State Nuclear Magnetic Resonance Spectroscopy. Biochemistry2015, 54 (14), pp 2335–2345; DOI: 10.1021/bi501552k

 

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