Tuesday, May 3, 2011
Lignocellulosic biomass is a potential renewable resource for production of fuels and chemicals that can replace petroleum-based fuels and chemicals, providing enormous economical, social, and environmental benefits, including improved energy security and reduced greenhouse gas emissions. Significant advances have been made in reducing the cost of cellulases for bioethanol production; however, additional improvements in enzyme performance are needed to further reduce the cost of enzymes. One of the approaches pursued by Novozymes is to develop advanced enzyme systems for high-temperature saccharification of lignocellulosic biomass. High-temperature saccharification has numerous advantages over conventional enzymatic hydrolysis at 50ºC, including improved activity of thermostable enzyme mixtures at elevated temperatures, improved enzyme storage stability, decreased risk of microbial contamination, and reduced viscosity of biomass slurries. Hydrolysis efficiency of current Trichoderma reesei cellulase system on a per mg protein basis can be improved by improving biochemical performance of selected existing components or supplementing the T. reesei cellulase system with novel synergistic proteins that can function at elevated temperatures. So far, these approaches have been successfully applied to the development of improved and robust enzyme mixtures for hydrolysis of dilute-acid pretreated corn stover (PCS) provided by NREL within the US DOE co-funded Project DECREASE. The improved enzyme mixtures work faster and require lower protein loadings to achieve target cellulose conversion compared to our current cellulases, leading to reduced cellulase cost for biomass conversion. Ample experimental evidence suggests that, in addition to PCS, high-temperature saccharification can be a viable option for many other commercially relevant pretreated biomass residues.