Isolation and modification of nano-scale cellulose from organosolv-treated birch through the synergistic activity of LPMO and endoglucanases

Madhu Nair Muraleedharan,Anthi Karnaouri,Maria Piatkova,Maria-Ximena Ruiz-Caldas,Leonidas Matsakas,Bing Liu,Ulrika Rova,Paul Christakopoulos,Aji P Mathew

doi:10.1016/j.ijbiomac.2021.04.136

Abstract

Nanocellulose isolation from lignocellulose is a tedious and expensive process with high energy and harsh chemical requirements, primarily due to the recalcitrance of the substrate, which otherwise would have been cost-effective due to its abundance. Replacing the chemical steps with biocatalytic processes offers opportunities to solve this bottleneck to a certain extent due to the enzymes substrate specificity and mild reaction chemistry. In this work, we demonstrate the isolation of sulphate-free nanocellulose from organosolv pretreated birch biomass using different glycosyl-hydrolases, along with accessory oxidative enzymes including a lytic polysaccharide monooxygenase (LPMO). The suggested process produced colloidal nanocellulose suspensions (ζ-potential −19.4 mV) with particles of 7–20 nm diameter, high carboxylate content and improved thermostability (To = 301 °C, Tmax = 337 °C). Nanocelluloses were subjected to post-modification using LPMOs of different regioselectivity. The sample from chemical route was the least favorable for LPMO to enhance the carboxylate content, while that from the C1-specific LPMO treatment showed the highest increase in carboxylate content.

Highlights

Nanocellulose is considered as one of the key value added products in the emerging market of biodegradable, green polymers
For the isolation of nano-scale cellulose from organosolv pretreated birch, disruption and removal of the lignin-hemicellulose matrix took place through alkaline hydrolysis, as depicted in Fig. 1A, in order to obtain a cellulose-rich pulp, which was subjected to hydrolysis for the removal of amorphous regions leaving behind the highly crystalline areas
Regarding the thermal stability properties of the samples, the results shown on Fig. 4 indicate a decreased thermostability of all three samples (NcCA, NcEE and NcELE) after post-treatment with both lytic polysaccharide monooxygenase (LPMO), and this trend is more profound in case of MtLPMO9H

Summary

Introduction

Nanocellulose is considered as one of the key value added products in the emerging market of biodegradable, green polymers. Nanocellulose can be described as cellulose particles with at least one of their dimensions, often diameter, in nanometric scale (below 100 nm) [2,3]. It can be produced from almost any cellulose-rich material found in nature, such as tunicates and plant-based lignocellulosic biomass [4,5]. The latter has attracted particular interest for nanocellulose production due to its high availability and low cost compared to other sources [6].

Methods

Results

Conclusion