Multiscale investigation on the chemical and anatomical changes of lignocellulosic biomass for different severities of hydrothermal treatment

The chemical changes sustained by lignocellulosic biomass during hydrothermal treatment are reflected at multiple scales. This study proposes to benefit from this multiscale nature in order to provide a global understanding of biomass alterations during hydrothermal treatment. For this purpose, complementary imaging techniques-confocal Raman microscopy and X-ray nano-tomography-analysed by image processing and coupled to chemical measurements were used. This unique combination of analyses provided valuable information on topochemical and morphological changes of poplar samples, without the artefacts of sample preparation. At the cell wall level, holocellulose hydrolysis and lignin modifications were observed, which corresponded to anatomical modifications observed at higher scales. Overall, after treatment, samples shrank and had thinner cell walls. When subjected to more severe pre-treatments, cells were disrupted and detached from adjacent cells. Anatomical changes were then used to obtain quantitative indicators of the treatment severity. The effects of treatment at different scales can thus be quantitatively connected in both directions, from micro to macro and from macro to micro.

Automated summary

This study used a multiscale approach combining confocal Raman microscopy and X-ray nano-tomography to investigate the chemical changes and structural effects of lignocellulosic biomass during hydrothermal treatment. The results showed that holocellulose hydrolysis and lignin modifications were observed at the cell wall level, leading to shrinkage and thinner cell walls in the samples. Moreover, more severe pre-treatments resulted in cell disruption and detachment, with anatomical changes providing quantitative indicators of treatment severity.