Decrystallization of Oligosaccharides from the Cellulose 1 beta Surface with Molecular Simulation

Bundles of cellulose polymers in plant cell walls exhibit a robust network of hydrogen bonds and hydrophobic interactions that must be overcome to decrystallize and hydrolyze the individual polymers to sugars. To investigate the molecular interactions that impart recalcitrance and insolubility to cellulose, we use simulation to determine the decrystallization work, a fundamental, yet experimentally inaccessible measurement, of cello-oligomers from the middle and edge of the hydrophobic face of cellulose Iβ. We demonstrate that cellobiose and cellotetraose decrystallization work does not depend on the position of the oligomer on the crystal surface but that larger oligomers are more difficult to decrystallize depending on the number of intralayer neighbors due to a larger number of stabilizing intralayer hydrogen bonds. The presented results are relevant to mesoscale, morphology-based models of cellulose deconstruction, understanding the molecular details of cellulose decrystallization and insolubility, and quantifying the oligomer length scale upon which short cellulose chains become inhibitory to enzymatic deconstruction of cellulose.