Flagship Theme: Plant cell walls in relation to biorefining

Flagship leaders: Prof Markus Pauly and Prof Sarah Hake

Desk researcher: Dr Ralf Möller

See the publications section for reports and presentations from this theme.

Summary

All plants contain cell walls, where most of the assimilated atmospheric carbon dioxide is deposited. Thus, plant cell walls represent the most abundant renewable resource present on this planet. Use of this reserve is constrained by a major bottleneck: the ability to fractionate the raw materials into easily accessible, industry-relevant components and precursors, for example, use in biofuel production.

User/Consumer benefit

The benefits of unlocking products from wall biomass are diverse, with major positive impact throughout supply chains from growers and processors to end-users and consumers.

Fossil reserves are finite; as supply decreases, the cost of petrochemical-based products, such as fuel, plastics and pharmaceuticals, will increase. Hence, cost-effective processes of biorefining for production of alternative materials will need to be developed to reduce dependence on fossil fuels. Work on plant cell walls can lead to other benefits as the properties of wall based materials are enhanced. Examples of such improvements include increased textile fibre yields, length and strength. Long-term benefits will have a significant positive impact on the environment and the economy as society decreases reliance on diminishing hydrocarbon reserves.

Scientific challenge

Plant cell walls have naturally evolved to resist breakdown from mechanical and microbial forces, precisely the processes needed for efficient, cost-effective biorefining. Unlocking the components in these biomaterials represents a massive scientific and technical challenge. The programme therefore has to be multidisciplinary and consist of an integrated set of projects, bringing together expertise in areas of:

1. chemistry of cell wall polymers, particularly the lignins, microcrystalline cellulose, hemicelluloses and pectins;
2. cell biology of the wall, to define organisation of the polymers in a cell, tissue, organ- and species-specific analysis;
3. bioprocessing of the raw material, to design novel and more efficient fractionation systems;
4. enzyme biochemistry and technologies of hydrolases involved in cell wall degradation;
5. genomics, proteomics and metabolomic analysis of cell wall biosynthesis and metabolism to devise new plant breeding strategies for the production of raw materials enhanced for biorefining.

The challenge is of such magnitude and multi-disciplinarity that it will require joint and co-ordinated action of experts in the US and the EU.

Economic benefits and risk analysis

The Flagship Theme is aimed specifically at decreasing the current economic risks associated with biorefining, which include the expense and continuing difficulties of efficient fractionation of biomass. Chemical industries will not switch from existing hydrocarbon feedstocks and associated supply chains until economic and environmental drivers are positive. Outputs from the pre-market Flagship Theme should increase these drivers to a point at which a major directional change is induced and can be further developed by the industries concerned. The use of GM versus non-GM technologies for production of biomass optimised for biorefining, will be analysed separately for the US and EU, given the different crops and processing infrastructure that already exist and different sociological attitudes to GM technologies.

Private sector involvement

The project will try to involve the private sector, such as seed companies, ethanol producers, plastics /  chemical producers, polymer industries and enzyme companies. The private sector will help fund, regulate and promote field studies based on fundamental lab developments. Thus, the project will consider all steps from fundamental research to field demonstration and biomass processing. Intellectual property management must be well defined and transparent so that society fully benefits from these discoveries. Funding will be precompetitive and not include marketing costs.

Products from plant cell walls

The following diagram shows that there is a large range of products that can be developed from plant cell walls. This flow scheme is modified from: Kamm B, Kamm M, Gruber PR, Kromus S (2006) Biorefinery systems – an overview. In: Biorefineries – industrial processes and products. Eds. Kamm B, Gruber PR, Kamm M; Wiley-VCH Verlag Weinheim.

		Lignocellulosic Feedstock
Lignin "Phenol polymer"		Cellulose "Glucose polymer"				Hemicellulose "Pentose–hexose polymer"
Lignins (oligomers, polymers)		Cellulose		Glucose		Xylose (and other sugars)
Emulsifiers		Fibres		Fuels		Polymers
Binders		Microfibres		Solvents		Resins
Adhesives		Nanocomposites		Polymers		Solvents
Novel products		Novel products		Novel products		Novel products

Images of plant cell walls

Pine needle plant cell walls seen under a light microscope

Model of the cell wall structure of a softwood tracheid Source: Fengel D, Wegener G (1989) Wood – Chemistry, Ultrastructure, Reactions. Walter de Gruyter, Berlin, New York.