Monday, April 30, 2007 - 10:10 AM

Molecular modeling investigation of non-reaction factors in the enzymatic hydrolysis of cellulose

Suma Peri, Muhammad Nazmul Karim, and Rajesh Khare. Chemical Engineering, Texas Tech University, 6th and Canton, MS: 43121, Lubbock, TX 79409

One of the bottlenecks in the production of biofuels using the biochemical platform is the recalcitrance of the cell wall of the lignocellulosic biomass.  A key step in this process is the enzymatic hydrolysis.  This research deals with the fundamental studies to investigate the “non-reaction” factors, which affect the enzymatic hydrolysis. The sensitivity analysis performed on kinetic parameters derived from our previous experiments on enzymatic hydrolysis of crystalline and non-crystalline celluloses showed the effect of different compositions of the enzymes on the maximum glucose yield. As the available enzyme compositions are almost at optimal condition, there is a need to understand the behavior of the substrate – enzyme – water systems.

 Enzymatic depolymerization of the insoluble cellulose involves the action of cellulases in the removal of the glucose chains from the surface of the crystal structure. Therefore, molecular level understanding of the properties of cellulose that provide resistance to the depolymerization will be helpful in removing the bottlenecks in the enzymatic hydrolysis process. Hydrolysis of semi-crystalline cellulose by cellulase enzymes is a solid-liquid heterogeneous reaction. Such a reaction is strongly affected by the non-reaction resistances caused most notably by the presence of the crystalline structure. These non-reaction factors include: interfacial area; diffusion of enzyme, substrate and product; and adsorption of enzyme onto non-cellulosic components.  Molecular dynamics simulations are employed to study the cellulose-water and cellulose-cellulase systems. Simulation results are used to quantify the non-reaction resistances in terms of the interfacial structure and diffusion in the system.