Unveiling the Variability and Multiscale Structure of Soybean Hulls for Biotechnological Valorization

Soybean hulls (SBH) are an important agroindustrial residue that is highly susceptible to cellulolytic enzymatic digestion. The multiscale structure of this biomass should be able to inform on the origins of its digestibility, but such relationships are currently unknown. This work employs multimodal techniques to learn SBH variability and multiscale structure. Tissue-scale images obtained by electron microscopy, X-ray microtomography, and Raman spectromicroscopy reveal tissue ruptures, lignin localized in the hilum region, and oriented, quite pure cellulose in palisade and hourglass cells of the extra-hilar region. Such specificities of SBH cellulose are reinforced by X-ray diffraction showing cellulose crystallites similar to 20% wider than in typical lignocellulosic biomass. SBH are also remarkably more porous than other lignocellulosic feedstocks in the critical pore size (> similar to 10 nm) for enzyme accessibility. Enzymatic hydrolysis confirmed the low recalcitrance of SBH, demonstrating high yields (e.g., 80% glucose) without SBH pretreatment. These results provide a basis for rationalizing the low recalcitrance of SBH, paving the way for novel developments in SBH biotechnological valorization.