Isolation of Pure Lignin and Highly Digestible Cellulose from Defatted and Steam-Exploded Cynara cardunculus

Abstract

In this work, a three-step approach to isolate the main components of lignocellulosic cardoon, lignin and cellulose, was investigated. The raw defatted biomass, Cynara cardunculus, after steam explosion was subjected to a mild organosolv treatment to extract soluble lignin (L1). Then, enzymatic hydrolysis was performed to achieve decomposition of the saccharidic portion into monosaccharides and isolate residual lignin (L2). The fractionation conditions were optimized to obtain a lignin as less degraded as possible and to maximize the yield of enzymatic hydrolysis. Furthermore, the effect of the use of aqueous ammonia as an extraction catalyst on both fractions was studied. Each fraction was characterized by advanced techniques, such as elemental analysis and 31 P nuclear magnetic resonance (NMR), 13 C− 1 H two-dimensional (2D)-NMR, attenuated total reflectance-Fourier transform infrared (ATR-FTIR), and UV−vis spectroscopies for lignin and X-ray diffraction (XRD), Klason compositional analysis, elemental analysis, and ATR-FTIR spectroscopy for cellulose-rich fractions. The impact of the cellulose-rich fraction composition and crystallinity was also correlated to the efficiency of the hydrolysis step, performed using the enzymatic complex Cellic CTec3.

Humic Acid-Functionalized Lignin-Based Coatings Regulate Nutrient Release and Promote Wheat Productivity and Grain Quality

“…In the current study, lignin extracted from Alfa plant was characterized before and after functionalization using solid-state 13 C NMR analysis in order to determine its chemical structure, the linkages between its units as well as the detailed changes in its structure after functionalization. The spectra of unmodified and modified lignin are presented in Figure , and the different signal assignments were obtained by comparison to the literature − and are listed in Table . Furthermore, the main lignin substructures are illustrated in Figure .…”

Steam Explosion-Based Method for the Extraction of Cellulose and Lignin from Rice Straw Waste

“…This preliminary study lays the groundwork for future endeavours in lignin purification and underlines the efficacy of the optimised steam explosion conditions in lignin extraction from rice straw [8,48,49].…”

“…The solid residue is filtered and washed several times in order to standardise the condition of the biomass before oxidation, ensuring consistency in our experimental results. The supernatant from this step, a lignin-rich solution, is reserved for further extraction, fractionation, and purification, thereby recovering the entire biomass [43,48,49]. The effectiveness of the cellulose fibre extraction depends on the swelling of the cellulose, as well as the softening and/or removal of the lignin induced by the steam treatment.…”

“…The four spectra show different peaks that can be correlated with lignin content. These include the aromatic skeletal vibrations around 1500 cm −1 , the -C-O stretching indicative of guaiacyl and syringyl lignin units, and the -CH stretching which suggests aliphatic hydrocarbons [49]. The prominence of -OH stretching near 3400 cm −1 suggests a high concentration of phenolic and aliphatic OH groups, typically abundant in lignin [76].…”