Identifying novel genes to improve lignocellulosic biomass for biofuel applications

Lowering the costs of producing bioethanol from lignocellulosic biomass is imperative for its commercialization. One approach of doing so is to produce crops that are more susceptible to hydrolysis in order to reduce pre-processing and enzyme inputs. To this end, we are using a forward genetic approach with the objective of identifying novel genes that affect the digestibility of plant biomass. We have screened a chemically mutagenised population of the model grass Brachypodium distachyon (produced by INRA, Versailles) for improved saccharification with industrial cellulases. This revealed 12 mutant lines with heritable increases in saccharification. Characterization of these 12 mutants revealed a range of different alterations in cell wall composition, including significant changes in lignin, hemicellulose, cellulose and ferulic acid content and also in lignin composition. Interestingly, a number of the mutant lines showed no change in lignin content. These results show that saccharification can be significantly improved through a number of distinct modifications of the cell wall, giving the potential for combining more than one of these modifications in biofuel crops to obtain even higher ethanol yields. Furthermore, the mutations seem to have little effect on plant phenotype, and mechanical strain tests revealed that none of the mutants showed a reduction in stem strength or stiffness compared to WT, an important trait for crop field performance. Current work is focussed on mapping the responsible mutations and characterisation of the mutated genes. This will enable subsequent examination of orthologous genes in the relevant cereal and grass crops used for biofuel production.