Integrated Production of Cellulose Nanofibrils and Cellulosic Biofuel by Enzymatic Hydrolysis of wood Fibers

One key barrier to converting woody biomass to biofuel through the sugar platform is the low efficiency of enzymatic cellulose saccharification due to the strong recalcitrance of the crystalline cellulose. Significant past research efforts in cellulosic biofuels have focused on overcoming the recalcitrance of lignocelluloses to enhance the saccharification of the recalcitrant cellulose. However, in this work [1,2], we demonstrate the conversion of recalcitrant cellulose into cellulosic nanomaterials, which have attracted a great deal of attention recently due to their unique properties and remarkable strength. Significant levels of sugars can be readily hydrolyzed from wood pulp, leaving yields of cellulosic solid substrate of 60%–90%. The crystallinity index of the recalcitrant cellulose was found to be higher than that of the starting pulp, verifying that enzymatic hydrolysis occurs preferentially on amorphous cellulose. Cellulose nanofibrils (CNFs) were produced from the recalcitrant cellulose using various mechanical refining approaches, and the morphology of the CNFs varied drastically depending on the level and method of refining. Extensive hydrolysis and mechanical disintegration resulted in CNFs with morphology similar to cellulose nanocrystals, which are discrete rod-like nanoparticles of highly crystalline cellulose. CNF films created in this research show good mechanical properties and transparency, and their use as composite reinforcements is being investigated.