Isolation and Surface Modification of Nanocellulose: Necessity of Enzymes over Chemicals

Abstract

Nanocellulose is an emerging sustainable biomaterial with exceptional physicochemical properties. It can be isolated from inexpensive renewable cellulosic biomass. Wood cellulose is the most extensively used biomass for the isolation of nanocellulose. Yet, owing to their hydrophilic nature, their utilization is restricted to applications involving hydrophilic or polar media, which limits their exploitation. With the presence of a large number of chemical functionalities within their structure, these building blocks provide a unique platform for significant surface modification through various methods. On the other hand, significantly used hazardous chemicals make the process environmentally unfriendly. Furthermore, recovery of used chemicals and toxicity of final products are the biggest challenges. To overcome these problems, the enzymatic approach is an emerging trend for isolation and surface modification of nanocellulose. This review assembles current knowledge in the research and development of nanocelluloses from cellulosic biomass and emphasizes the enzymatic routes developed so far for isolation, production, and functionalization.

Nanocellulose: From Fundamentals to Advanced Applications

“…Surface functionalization can be carried out during the preparation step or post-production of nanocellulose (Wei et al, 2017). These modifications lead to attaining desirable properties, which, in turn, enhance their effectiveness for a given application (Lin et al, 2012;Afrin and Karim, 2017;Liang et al, 2020;Tao et al, 2020). Through the incorporation of any chemical functionality, the surface of a nanocellulosic material can be modified the way it reacts with foreign substances (George and Sabapathi, 2015).…”

“…According to previous literature (George and Sabapathi, 2015;Afrin and Karim, 2017;Daud and Lee, 2017;Huang et al, 2020), the surface of cellulose nanocrystals can be chemically modified using numerous methods, mainly covalent surface modification including sulfonation, polymer grafting, oxidation, esterification, nucleophilic substitution, etherification, silylation, and carbamation. In a recent study, polyacrylamide has been grafted onto cellulose nanocrystals (CNC) to integrate into poly(vinyl alcohol) (PVA) employing a solution casting method to reinforce nanocomposite films.…”

“…Some of the physical surface functionalization techniques may include electric discharge (plasma treatment), ultrasonic treatment, irradiation, and surface fibrillation (Islam et al, 2013). Enzymes can also be used to modify the surface of nanocellulose, for instance, Afrin and Karim (2017) employed two approaches in their study; (a) direct modification, where the enzyme directly gets in contact with nanocellulose, and (b) indirect enzymemediated modification. They concluded that the enzymatic approach to produce nanocellulose and to further functionalize them is a viable greener modification method compared to chemical modification route.…”

In vivo hepatotoxicity of chemically modified nanocellulose in rats

“…Specifically, during modification, certain functional groups are introduced to the parent molecule to increase the amount of stable positive or negative charges for better dispersion and the improvement of compatibility when combined with hydrophobic matrices. 4,5 Wei et al 6 functionalized CSN by transesterification with fatty acid methyl ester of canola oil. In other studies, surface modification of CSN was achieved in aqueous and organic media using octadecyl, monoallyl-poly (ethylene glycol), benzyl, and propargyl triazinyl derivatives.…”

Progress of novel techniques for lightweight automobile applications through innovative eco-friendly composite materials: A review

“…Therefore, the utilization of enzymes above chemicals is a suitable method to free pretreated cellulose from lignin and hemicelluloses, respectively. 136,137…”