Understanding the Molecular Basis for Cellulose Recalcitrance with Atomistic Simulation

Cellulose-degrading organisms in the biosphere have evolved a complex cocktail of enzymes for overcoming biomass recalcitrance. Most enzyme cocktails contain both processive and non-processive cellulases, which are able to de-crystallize single cellulose strands and hydrolyze the glycosidic linkages along a cellulose chain. A ubiquitous step that both processive and non-processive cellulases must accomplish is cellulose de-crystallization, for which there is an inherent thermodynamic penalty. Here, we measure the thermodynamic cost for cellulose de-crystallization as a function of cellulose morphology and polymorph at the atomic scale with molecular simulation. Our results indicate how enzymes may have evolved to degrade biomass in the biosphere at the molecular-level and suggest directions for increasing the enzymatic accessibility for cellulose digestion in biofuels applications.