Chapter 2: Challenges and Opportunities for Using Wheat for Biofuel Production

Wheat is an attractive raw material for biofuel production, with over 600 million tonnes grain being harvested annually, and a potentially similar amount of straw available as a bi-product. Wheat whole grain has a starch content of about 70% dry weight, but about 10% consists of cell wall polysaccharides which are not currently saccharified for fermentation and limit the quality of the residual grain for livestock feed. The major cell wall polysaccharides in wheat grain are arabinoxylans, with smaller amounts of β-glucans. However, in outer grain tissues (bran) and straw the dominant polysaccharides are cellulose and glucuronoarabinoxylan, with large quantities of lignin. We discuss our current knowledge of arabinoxylan synthesis in wheat and how this can be exploited by manipulating the expression of key biosynthetic enzymes to change the structures and interactions of the cell wall xylans to improve the yield of biofuels from whole grain and straw.