(678f) Calculation of Free Energy Involved in Saccharification of Cellulose Using Molecular Dynamic Simulations

Enzymatic hydrolysis of cellulosic substrates involves the removal of chains of sugar molecules from the surface of the cellulose fibers. During the hydrolysis reaction, short cello-oligosaccharides which are the reaction intermediates, get attached to the cellulose surface, thus lowering the overall rate of the hydrolysis process. The detailed molecular mechanisms involved in the hydrolysis of cellulose fibers are investigated in this research using molecular simulations.

We performed free energy calculations for the separation of a cellobiose pair as well as for the process of separation of a cellobiose molecule from the cellulose crystal surface in the presence of water. The potential of mean force (PMF) profile for the separation of the cellobiose pair exhibited a single primary minimum at a separation distance of 4.75 Å. On the other hand, the PMF profile for the separation of a cellobiose molecule from the cellulose crystal surface showed a well defined minimum and a weak maximum at distances of 5.65 Å and 7.65 Å respectively. Due to the increased number of interactions of the cellobiose molecule with the cellulose crystal surface, the well depth of the free energy profile obtained in the case of cellobiose-cellulose surface separation was an order of magnitude higher than that for the cellobiose pair separation. Results will also be presented for the dynamics of a cellobiose molecule near a cellulose crystal surface.