Anaerobic Biodegradation of Cellulose-Xylan-Lignin Nanocomposites as Model Assemblies of Lignocellulosic Biomass

In order to determine the parameters influencing lignocellulosic biomass biodegradability, binary and ternary model systems were constructed, consisting of cellulose nanowhiskers gel, xylan matrix derived from lignocellulosic plants and synthetic lignin. The adsorption of two xylan polymers with different arabinose/xylose ratios (Ara/Xyl) on the cellulose nanowhiskers resulted in the synthesis of nanocomposites each of different Ara/Xyl ratios and crystallinity indexes. Organized and associated cellulose-xylan-lignin nanocomposites were formed following the polymerization of guaiacyl (G) and syringyl (S) lignin monomers using a peroxidase/H2O2 system in cellulose nanowhiskers-xylan gel. The anaerobic digestion of cellulose nanowhiskers, xylans and cellulose-xylan nanocomposites indicated that the biomethane production depended strongly on the xylan Ara/Xyl ratio and on the cellulose crystallinity. However, the anaerobic digestion of cellulose-xylan-lignin nanocomposites showed that the digestion rate decreased significantly in the presence of lignin. Moreover, there was an even more considerable decrease in digestion rate in the presence of GS-type lignin compared to G-type lignin.