New tools for the realization of cost-effective liquid biofuels from plant biomass (revised costs)

The production of liquid biofuels from lignocellulosic biomass offers the potential to provide liquid transportation fuels in an environmentally benign manner without compromising food security. Lignocellulose is largely composed of polysaccharides that can be converted into simple sugars and used to produce alcohols such as ethanol and butanol by microbial fermentation. Production of such liquid biofuels from plant biomass is currently hampered by the cost of converting lignocellulose into fermentable sugars (saccharification). There is a clear need for new and better enzymes for lignocellulose saccharification. A number of animals such as termites can survive on a diet of lignocellulose, suggesting they have overcome the problem of obtaining sugars from this recalcitrant substrate. 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 an effectively 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 programme of work aims to identify the key mechanisms and components of lignocellulose digestion in Limnoria, in order that we can apply principles and enzymes from this process in order to enhance industrial lignocellulose saccharification.