Biomass to bioethanol
Currently bioethanol is produced by fermentation of sugars from cane and beet, or hydrolysed starch, and as such competes with food production for raw materials. However, as the UN estimates that by 2025 we will no longer produce enough food to feed the growing population, there is increasing pressure to find alternatives.
Second generation biofuels will be made from the whole plant if desired, rather that just a specific part. For example, the stems of wheat plants (i.e. straw) contain as much sugar (in the form of polysaccharides like cellulose) as do the grains (in the form of starch). Conversion of the polysaccharides in the straw into sugars would present a previously untapped source of sugars for bioethanol production with no impact on food supply. Wheat is just one example; there are millions of tonnes of agricultural waste produced each year. However, production of biofuels from plant biomass is currently hampered by the cost of converting lignocellulose into fermentable sugars (saccharification).
Projects in this area include:
Liquid biofuels from plant biomass
Funded by the BBSRC Bioenergy Initiative
Simon McQueen-Mason and Neil Bruce (CNAP) and Simon Cragg (Portsmouth University).
Video feature: bugs to biofuel
The aim of this project is to discover new and better enzymes for lignocellulose saccharification to reduce the costs of liquid biofuel manufacture. A potential source of these enzymes exist in nature as a number of animals such as termites can survive on a diet of lignocellulose, suggesting they have overcome the problem of obtaining sugars from lignocellulose. These organisms generally rely on a population of bacteria and protists in their digestive tract that help to digest the lignocellulose.
An exception to this rule is found in the Limnoriidae (also known as gribble): small crustacean wood borers from the marine environment. These animals can survive on a diet of lignocellulose and are unusual in having a sterile digestive tract. This suggests that not only can Limnoria digest lignocellulose with their own enzymes, but that conditions within the digestive tract, associated with lignocellulose digestion, prevent microbes from becoming established.
The unusual nature of lignocellulose digestion in Limnoria indicates a great potential for uncovering new insights and approaches to saccharification and new enzymes and genes for industrial applications. By analogy, the termite digestive tract can be seen as a complex microbial reactor for lignocellulose digestion, whereas the Limnoria gut is an enzyme reactor, and thereby much closer in its nature to current industrial systems.
The transcriptome of the Limnoria gut has been determined by deep sequencing and an entire suite of hydrolytic enzymes have been discovered and patented in this research programme.
Improving plant cell walls for use as a renewable industrial feedstock (RENEWALL)
An EC funded consortium of 18 partners across Europe and the US.
Project Co-ordinator: Professor Simon McQueen Mason
Plant biomass (or ‘lignocellulose’) is one of the greatest untapped reserves on the planet and is mostly composed of cell walls. Energy-rich polysaccharide polymers make up about 75% of plant cell walls and, in theory, these can be broken down to produce sugar substrates (saccharification) from which a whole range of useful products can be made (e.g. bioplastics, fine and bulk chemicals, food and feed ingredients), including bioethanol. It has been estimated that sufficient potential exists in current plant biomass production in the US to replace 30% of petroleum consumption without any impact on food production.
Even more value can be added by using integrated processing systems that allow multiple different products to be produced from the same biomass: the biorefinery concept. However, the complex structure of cell walls, consisting of a network of cellulose microfibrils and matrix polysaccharides (hemicellulose; pectin) encrusted by the phenolic polymer, lignin, makes them very resistant to degradation. Improving the ease and yield of cell wall saccharification represents the major technological hurdle that must be overcome before the full vision of the plant-fuelled biorefinery can be realized.
The RENEWALL project brought together leading cell wall scientists and plant breeders from Europe and the USA to work together in overcoming this fundamental technical bottleneck in the development of biomass as a renewable biorefinery feedstock.
Secret to making renewable energy from wood? The digestive system of the gribble may hold the key!
2 new Networks in Industrial Biotechnology awarded! Congratulations to Ian Graham and Simon McQueen-Mason, who will each lead a phase II NIBB.
Poppy genome decoded DNA code of the opium poppy genome determined.
Strengthening links with India: 2 major new research projects Funding secured by CNAP PIs.
CNAP, Department of Biology, University of York, Wentworth Way, York YO10 5DD, UK