There is considerable interest in understanding how hemicellulose and cellulose interact in the plant cell wall, both from the perspective of studying cell wall synthesis, but also for understanding the fate of these polymers during biomass deconstruction. However, it is difficult to study the molecular interactions between these polymers in situ due to the inherent complexity of the plant cell wall. Model hemicellulose-cellulose composites, that mimic plant cell wall polymer interactions were prepared by synthesizing deuterated bacterial cellulose in the presence of glucomannan or xyloglucan. We used a multimodal approach that combined small-angle neutron scattering, X-ray diffraction and sum frequency generation spectroscopy data, to provide new insights into changes in cellulose structure due to presence of and the subsequent removal of hemicellulose during dilute acid pretreatment. The macrofibril dimensions of the pretreated cellulose alone were smaller but with similar entanglement of macrofibrillar network as native cellulose. In addition, the crystallite size dimension along the (010) plane increased. Glucomannan-cellulose underwent similar changes to cellulose, except that the macrofibrillar network was more entangled after DAP. Conversely, in xyloglucan-cellulose the macrofibril dimensions and macrofibrillar network were relatively unchanged after pretreatment but the cellulose Iβ content was increased. Our results point to a tight interaction of xyloglucan with microfibrils while glucomannan only interacts with macrofibril surfaces. This study provides insight into roles of different hemicellulose-cellulose interactions and may help in improving pretreatment processes or engineering plants with decreased recalcitrance.

Hemicellulose-cellulose composites reveal differences in cellulose organization after dilute acid pretreatment

2019 Spring National Meeting

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