Biodegradation of Functionalized Nanocellulose

Abstract

Nanocellulose has attracted widespread interest for applications in materials science and biomedical engineering due to its natural abundance, desirable physicochemical properties, and high intrinsic mineralizability (i.e., complete biodegradability). A common strategy to increase dispersibility in polymer matrices is to modify the hydroxyl groups on nanocellulose through covalent functionalization, but such modification strategies may affect the desirable biodegradation properties exhibited by pristine nanocellulose. In this study, cellulose nanofibrils (CNFs) functionalized with a range of esters, carboxylic acids, or ethers exhibited decreased rates and extents of mineralization by anaerobic and aerobic microbial communities compared to unmodified CNFs, with etherified CNFs exhibiting the highest level of recalcitrance. The decreased biodegradability of functionalized CNFs depended primarily on the degree of substitution at the surface of the material rather than within the bulk. This dependence on surface chemistry was attributed not only to the large surface area-to-volume ratio of nanocellulose but also to the prerequisite surface interaction by microorganisms necessary to achieve biodegradation. Results from this study highlight the need to quantify the type and coverage of surface substituents in order to anticipate their effects on the environmental persistence of functionalized nanocellulose.

Degradation of Cellulose Derivatives in Laboratory, Man-Made, and Natural Environments

“…Similar trends were observed during degradation of the same CNF materials during aerobic biodegradation with inoculum from aerobic wastewater. 64 …”

“… Normalized biogas production during anaerobic degradation of unmodified and modified CNF. Reprinted from ref ( 64 ). Copyright 2021 American Chemical Society.…”

Ultrasonic cavitation: An effective cleaner and greener intensification technology in the extraction and surface modification of nanocellulose

“… Modification Nanocellulose type Ultrasonic Equipment Ultrasonic Conditions Ref. Purpose Power (W) Time (min) Freq (kHz) Temp (˚C) Sulphonation CNC Probe Pre-treatment 750 15 25 – [141] CNC Probe Post-treatment 800 5 – 45 [218] CNC Probe Post-treatment 400 120 24 10 [83] CNC Probe Post-treatment – 60 22 – [119] CNC Bath Post-treatment 350 15 53 – [219] TEMPO-mediated oxidation CNF Bath Synchronous 1000 60 170 14 [146] CNF Probe Post-treatment 300 20 – – [175] CNC Probe Post-treatment 400 30 20 – [160] Etherification CNF Bath Pre-treatment – 240 – – [232] ...…”

The Role of Eucalyptus Species on the Structural and Thermal Performance of Cellulose Nanocrystals (CNCs) Isolated by Acid Hydrolysis

“…From a technological perspective, the CNCs have been used alone or in combination with other materials. Such is the case of polymer biocomposites, in which CNCs act as fillers for mechanical reinforcement purposes, along with permeability modulator of matrices, while maintaining biodegradability [ 16 , 17 , 18 ]. Compared to other inorganic reinforcing fillers, the CNCs are widely available, easily processable due to their non-abrasive nature, and allow for high filling levels and significant cost-savings [ 19 ].…”