3Laboratory of Renewable Resources Engineering

The overall cost-efficiency of ethanol production from ligno-cellulosic biomass needs to improve in order for this to become an economically attractive process. We are using an integrated approach that incorporates both stover composition and processing conditions to make the stover-to-ethanol conversion more cost-effective. We are investigating the potential of maize and sorghum brown midrib mutants as a source of ligno-cellulosic biomass. The lignin composition and ultrastructure of secondary cell walls in these mutants are different as a result of genetic changes, while the reduction in total biomass is only minimal. We have obtained a considerably higher (50%) yield of fermentable sugars after enzymatic hydrolysis of stover from certain brown midrib mutants. In addition, we are exploring the use of enzyme mimetics to reduce the cost associated with the hydrolysis of cell wall carbohydrates. This is done in conjunction with the different sources of stover, so that the efficacy of enzyme mimetics can be related to stover composition, and vice versa.