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Background: The development of technological routes to convert lignocellulosic biomass to liquid fuels requires an in-depth understanding of the cell wall architecture of substrates. Essential pretreatment processes are conducted to reduce biomass recalcitrance and usually increase the reactive surface area. Quantitative three-dimensional information about both bulk and surface structural features of substrates needs to be obtained to expand our knowledge of substrates. In this work, phase-contrast tomography (PCT) was used to gather information about the structure of a model lignocellulosic biomass (piassava fibers). Results: The three-dimensional cellular organization of piassava fibers was characterized by PCT using synchrotron radiation. This technique enabled important physical features that describe the substrate piassava fibers to be visualized and quantified. The external surface area of a fiber and internal surface area of the pores in a fiber could be determined separately. More than 96% of the overall surface area available to enzymes was in the bulk substrate. The pore surface area and length exhibited a positive linear relationship, where the slope of this relationship depended on the plant tissue. Conclusions: We demonstrated that PCT is a powerful tool for the three-dimensional characterization of the cell wall features related to biomass recalcitrance. Original and relevant quantitative information about the structural features of the analyzed material were obtained. The data obtained by PCT can be used to improve processing routes to efficiently convert biomass feedstock into sugars. [ABSTRACT FROM AUTHOR]

pplication of in-situ microtomography to characterization of power law creep and creep damage in structural materials is presented. It is shown first that the successively reconstructed volumes are adequately monitoring the macroscopic sample shape and that microtomography is an optimal tool to characterize inhomogeneous specimen deformation. Based on a two-step image correlation technique the evolution of single voids is revealed and the basis of a pioneering approach to creep damage studies is presented. The method allows the unequivocal separation of three concurrent damage mechanisms: nucleation, growth, and coalescence of voids. The results indicate that growth rate of voids with equivalent diameters in the range of 2-5 mm is of about one order of magnitude higher than the prediction of continuum solid mechanics. Analysis of void coalescence points out the presence of two stable growth regimes related to coalescence between primary and secondary voids, respectively. [ABSTRACT FROM AUTHOR]

Alternative and renewable fuels derived from lignocellulosic biomass offer a potential alternative to conventional energy sources. Biorefinery feedstocks are usually pretreated with acid, alkali, or high temperature/pressure treatments before enzyme hydrolysis to yield glucose and other useful sugars for fermentation to ethanol. If plant cell walls are to be efficiently deconstructed by conversion technologies, then a detailed understanding of their structural organization in different length scales is required. Here, a novel imaging technique provided an opportunity to probe the deconstruction of the biomass structure by alkali pretreatments under mild operation condition. High-resolution phase-contrast tomography (PCT) provided unique aspects on the recalcitrance-related changes of physical structures spanning macro and micrometer length scales. This approach revealed that the thickness of the plant cell walls was considerable reduced on the whole particle. However, long cracks could be particularly observed crossing over the thin-walled parenchyma cells, making each the fibrovascular bundles totally or partially unattached and independent. Such particle fragmentation was responsible for increasing its external specific surface area about 10 times, while the total surface area of the inner porous structure only doubled in value. The PCT and imaging processing techniques can be applied to different processing routes for ethanol conversion, providing new insights into the underlying mechanisms of biomass deconstruction. [ABSTRACT FROM AUTHOR]