RICEFUEL: Engineering enzymes, bacteria and bioconversion processes for advanced biofuels from waste grain straw

点击翻译按钮获取中文摘要

The use of fossil fuels in the energy and chemical industries is no longer tenable; they represent a finite resource and their use results in carbon dioxide emission, which is a major cause of global warming. There is, therefore, an urgent need to find alternative sources of liquid fuels that are renewable and do not have an adverse effect on the environment. Lignocellulosic biomass is a promising substrate for biofuel production as it is not a food source, is more abundant than starch, and its use is carbon dioxide neutral. A significant limitation in the use of lignocellulosic biomass in the biofuel industry is its recalcitrance to enzymatic attack, and the lack of microbial strains capable of fermenting lignocellulosic-derived sugars into non-ethanol advanced biofuels, such as butanol and alkanes. The development of second generation, lignocellulose-based, biofuels is a global issue that is highly relevant to the economies of the UK and India. The research programme will focus on rice straw as the source of biomass. Our selection of this cereal waste product is based on several criteria: rice is the third biggest crop grown in the world and the major staple crop for most tropical nations. The case for developing biorefining technologies to generate fuels and chemicals is particularly compelling. Rice straw is produced in large quantities because tropical agriculture allows 2-4 crops per year to be produced. The use of rice straw in agriculture is particularly problematic as it is even less digestible than other cereal straws, and this severely limits its use as an animal feed, and this restricts its use to construction materials, animal bedding and cooking fires. Because of this rice straw, in the order of hundreds of millions of tons per year, are burned on the field in South and Southeast Asia alone to facilitate its disposal. Not only is straw burning a waste of a potentially valuable resource, but the process causes large scale emissions of black carbon, CO2 and methane. It is evident, therefore, that rice straw represents an excellent substrate for the biofuel sector. In this research programme we will 1) develop an enzyme cocktail optimised for rice straw deconstruction and (2) develop strains of Geobacillus, a bacterium whose metabolism can easily be modified, to produced advanced biofuels such as alkanes. These two streams of the programme we then be incorporated into a single process capable of producing high utility biofuels from rice straw.