Exploring Biomass Recalcitrance at the Petascale With Molecular Simulation

Joshua Vermaas, University of Illinois at Urbana-Champaign

Cheap and abundant biofuels will be needed to sustainably meet our future energy needs. The Cel7A enzyme from the fungus Trichoderma reesei (TrCel7A) has been isolated and used in industrial enzyme cocktails to degrade biomass into simple sugars, but specific scenarios have eluded experimental characterization. Through classical molecular dynamics simulations conducted during successive practicums at the National Renewable Energy Laboratory and Oak Ridge National Laboratory we investigate two such scenarios: one in which the cellulose fibril has been oxidized by a lytic polysaccharide monooxygenase (LPMO) and one in which a lignin-cellulose network is attacked by TrCel7A representative of post-pretreatment lignocellulosic biomass. We find that LPMO action stimulates TrCel7A processivity by reducing the work required for cellulose decrystallization by promoting the exposure of newly created chain termini into solution, although, depending on the resulting species, it may also increase product inhibition. Lignin inhibits function of TrCel7A by binding directly to the domain of TrCel7A responsible for cellulose binding as well as by occluding a large fraction of the cellulose surface and forming a dense mesh network that retards TrCel7A diffusion.

Abstract Author(s): Josh Vermaas, Michael Crowley, Christina Payne, Gregg Beckham, Loukas Petridis, Jeremy Smith