Enzymatically-Mediated Co-Production of Cellulose Nanocrystals and Fermentable Sugars

Abstract

Cellulose nanocrystals (CNCs) can be extracted from cellulosic materials through the degradation of non-crystalline cellulose domains in the feedstock via acid hydrolysis. However, the sugars released from the hydrolysis process cannot be easily recovered from the acid waste stream. In this study, cellulases were used to preferentially degrade non-crystalline domains with the objectives of recovering sugars and generating a feedstock with concentrated CNC precursors for a more efficient acid hydrolysis process. Filter paper and wood pulp substrates were enzyme-treated for 2-10 h to recover 20-40 wt % glucose. Substantial xylose yield (6-12 wt %) was generated from wood pulp. CNC yields from acid hydrolysis of cellulases-treated filter paper, and wood pulp improved by 8-18% and 58-86%, respectively, when compared with the original substrate. It was thought that CNC precursors accumulated in the cellulases-treated feedstock due to enzymatic digestion of the more accessible non-crystalline celluloses. Therefore, acid hydrolysis from enzyme-treated feedstock will require proportionally less water and reagents resulting in increased efficiency and productivity in downstream processes. This study demonstrates that an enzymatically-mediated process allows recovery of fermentable sugars and improves acid hydrolysis efficiency for CNC production.

Characterization of Cellulase-Treated Fibers and Resulting Cellulose Nanocrystals Generated through Acid Hydrolysis

“…We previously reported that there was no significant improvement in CNC yield (wt % acid hydrolyzed feedstock) from these feedstock as a function of time (except at 10 h) [31]. This finding indicates simultaneous hydrolysis of crystalline cellulose throughout the treatment period.…”

“…Samples of washed and freeze-dried fibers that were treated with a cellulase cocktail (NS 51129, Novozymes A/S, Bagsvaerd, Denmark) and CNCs isolated by acid hydrolysis (64% H 2 SO 4 w / w , 45 °C, 2 h) generated from experiments described in our previous study [31] were characterized. Sodium chloride was purchased from Fisher Scientific Company (Whitby, ON, Canada).…”

Effect of incorporation of microstructured carbonized cellulose on surface and mechanical properties of epoxy composites

“…A promising case of study could be represented by the comparison of spheres and rods particles. As reported by Bartoli et al ., carbon spheres can be produced by pyrolytic treatment of cellulose nanocrystals (CNCs) while carbon rods can be obtained by the same process using wasted cotton fibers (CFs) . Additionally, these materials are both composed by cellulose and pyrolytic reactivity and biochar residual groups are the same using the same pyrolytic conditions …”

Co-Production of Cellulose Nanocrystals and Fermentable Sugars Assisted by Endoglucanase Treatment of Wood Pulp

“…Endoglucanases have been shown to have relatively mild activity, which is suitable for hydrolysis of amorphous regions of cellulose without complete hydrolysis to glucose, while preserving the crystalline cellulose domain [ 21 , 22 ]. In a previous study from our group, we reported higher CNC yields and less acid consumption using cellulase-treated cellulose as crystalline-enriched feedstock for acid hydrolysis [ 32 ]. Furthermore, this enzyme treatment resulted in a sugar stream that could be fermented to biofuels such as ethanol.…”