Cellulosome Design for Cellulosic Ethanol
by Jiancong Xu
The recalcitrance of lignocellulosic biomass to enzymatic hydrolysis is a bottleneck in cellulosic ethanol production. One promising avenue for overcoming biomass recalcitrance is to understand and modify the properties of bacterial cellulosomes.
Cellulosomes are large extracellular enzyme complexs that are produced by anaerobic bacteria and can efficiently break down plant cell wall polysaccharides, such as cellulose, hemicellulose and pectin into sugars. The cellulosome complex consists of various kinds of enzymes arranged around a scaffolding protein that does not exhibit catalytic activity but enables the complex to adhere to cellulose.
The organization of the cellulosome is mediated by high-affinity protein-protein interactions between Type-I cohesin domains within the scaffolding proteins and complementary Type-I dockerin domains carried by cellulosomal enzymes.
Figure: Crystal structure of the Type-I cohesin-dockerin complex in a water box.
Computational modeling is essential to develop a full understanding of the assembly mechanism of the cellulosome and its ability in biomass digestion. Our initial goal is to explore the functional roles of specific domains and amino acid residues on the contact surface of the cohesin-dockerin complex by using molecular dynamics and free energy calculations.