Abstract
Cellulose nanomaterials are produced employing a multitude of methodologies including electrospinning, bacterial generation, acid digestion, and a variety of mechanical defibrillation techniques; the morphology of the nanomaterial produced is specific to the production process. Feedstocks range from various forms of woody biomass, to fungi, and have a great impact on the resulting product. The mechanical defibrillation technique, such as that employed in the present work, continuously breaks down cellulose fibers suspended in water via segmentation and defibrillation through grinding and refining. The process is typically operated until a desired level of fines is achieved in the resultant slurry of cellulose nanofiber (CNF), alternatively known as cellulose nanofibril. Mechanical defibrillation processes can be built to produce several liters in a small batch system or up to tons per day in a continuous pilot scale refiner system. In the present work a continuous system was developed with the capacity to produce 14 L of cellulose nanofiber slurry with consistent specifications and in a manner compliant with GMP/GLP protocols in order to be amenable to biomedical applications. The system was constructed within an ISO class 7 cleanroom and refining was performed on bleached softwood pulp suspension in purified water. This manuscript details the continuous grinding system, the processes employed to produce cellulose nanofiber, and characterizes the resultant cellulose nanofiber slurry and sheets formed from the slurry.
Highlights
Cellulosic nanomaterials are finding exponentially increasing popularity from a research and development, as well as a pre-commercialization, perspective (Trache et al, 2020)
Bacterial nanocellulose is excreted from bacteria of the genus Komagataeibacter, formerly Acetobacter, in a liquid growth medium (Abol-Fotouh et al, 2020); the dimensions of the fibers tend to be consistent, but are heavily dependent upon procedural parameters such as the bacteria employed, stirring rate, temperature, etc., (Moon et al, 2011; Tayeb et al, 2018) Electrospun cellulose nanofibers are characterized via diameters in the range of 5–100 nm and fiber lengths greater than 1 micron
Cellulose nanofiber (CNF) is being increasingly explored as a biodegradable, sustainable, and non-immunogenic material for biomedical applications (Nechyporchuk et al, 2016; Gorgieva and Trček 2019). As such it is critical that a process, or processes, be developed that enable production of cellulose nanofiber (CNF) in a manner that creates a high quality, reproducible material that may be sterilized in preparation for implantation, or otherwise used in animal/human applications
Summary
Cellulosic nanomaterials are finding exponentially increasing popularity from a research and development, as well as a pre-commercialization, perspective (Trache et al, 2020). The term is typically employed in reference to cellulosic materials composed of crystalline and/or amorphous regions with fiber diameters less than 100 nm and fiber lengths less than or equal to several microns (Mokhena and John 2020). Bacterial nanocellulose is excreted from bacteria of the genus Komagataeibacter, formerly Acetobacter, in a liquid growth medium (Abol-Fotouh et al, 2020); the dimensions of the fibers tend to be consistent, but are heavily dependent upon procedural parameters such as the bacteria employed, stirring rate, temperature, etc., (Moon et al, 2011; Tayeb et al, 2018) Electrospun cellulose nanofibers are characterized via diameters in the range of 5–100 nm and fiber lengths greater than (and potentially very much greater) 1 micron. In particular an emphasis is placed on production of CNF that is amenable to use in biomedical applications and as such is produced in accordance with good manufacturing/good laboratory GMP/GLP practices
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