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

Dawit Beyene,Michael Chae,Frank Tosto,Christophe Danumah,David C. Bressler,Abayneh Getachew Demesa,Jing Dai

doi:10.3390/catal7110322

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.

Highlights

In recent years, the demand for print media products has been declining, especially in NorthAmerica [1], due to the ever growing use and popularity of electronic media
Cellulase cocktail treatment of filter paper and wood pulp over a course of time allowed for the recovery of a range of fermentable sugars that can offset cellulose nanocrystals (CNCs) production costs
The CNC yield from acid-hydrolyzed filter paper and wood pulp improved by 8–18% and 58–86%, respectively, from 2 to 10 h enzymatic treatment

Summary

Introduction

The demand for print media products has been declining, especially in NorthAmerica [1], due to the ever growing use and popularity of electronic media. The demand for print media products has been declining, especially in North. The pulp and paper industry is aiming to diversify to high value-added products such as cellulose nanocrystals (CNCs). Crystalline cellulose extracted in nanoscale dimensions of 3–5 nm width and 50–500 nm length are referred to as CNCs [3]. These cellulose crystals have been isolated from different sources such as wood pulp [4], cotton (WhatmanTM No 1 filter paper,) [5], tunicate (an aquatic invertebrate) [6], and bacteria [7]. CNCs are highly reactive and show a superior mechanical strength due to their large surface area as nanoparticles and high crystallinity, respectively [8]

Objectives

Results

Conclusion