Abstract
Lignocellulosic composite in corn stover is a candidate biofuel feedstock of substantial abundance and sustainability. Its utilization is hampered by resistance of constituent cellulose fibrils to deconstruction. Here we use multi-scale studies of pretreated corn stover to elucidate the molecular mechanism of deconstruction and investigate the basis of recalcitrance. Dilute acid pretreatment has modest impact on fibrillar bundles at 0.1 micron length scales while leading to significant disorientation of individual fibrils. It disintegrates many fibrils into monomeric cellulose chains or small side-by-side aggregates. Residual crystalline fibrils lose amorphous surface material, change twist and where still cross-linked, coil around one another. Yields from enzymatic digestion are largely due to hydrolysis of individual cellulose chains and fragments generated during pretreatments. Fibrils that remain intact after pretreatment display substantial resistance to enzymatic digestion. Optimization of yield will require strategies that maximize generation of fragments and minimize preservation of intact cellulosic fibrils.
Highlights
Lignocellulosic composite in corn stover is a candidate biofuel feedstock of substantial abundance and sustainability
Yields from enzymatic digestion are largely due to hydrolysis of individual cellulose chains and fragments generated during pretreatments
Materials pretreated with hot water, dilute acid and dilute acid plus iron sulfate exhibit a monotonic progression of saccharification yields
Summary
Hideyo Inouye[1], Yan Zhang[1], Lin Yang[2], Nagarajan Venugopalan[3], Robert F. Dilute acid pretreatment has modest impact on fibrillar bundles at 0.1 micron length scales while leading to significant disorientation of individual fibrils. It disintegrates many fibrils into monomeric cellulose chains or small side-by-side aggregates. Optimization of yield will require strategies that maximize generation of fragments and minimize preservation of intact cellulosic fibrils. Deconstruction efficiency is limited, by the recalcitrance of residual components[8,9], and improving yield requires a focus on the integrity of the cellulose fibrils themselves. Structural studies have provided insight into the nanoscale architecture of lignocellulose[10,11] and its reaction to pretreatments[12,13] but the molecular mechanism of deconstruction and the basis of recalcitrance remain obscure. USAXS from untreated samples exhibited characteristic diamond-shaped diffuse scattering with a sharp spike of intensity along the equator www.nature.com/scientificreports
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