The emergence of hybrid cellulose nanomaterials as promising biomaterials.

Cellulose nanomaterials (CNs) are promising green materials due to their unique properties as well as their environmental benefits. Among these materials, cellulose nanofibrils (CNFs) and nanocrystals (CNCs) are the most extensively researched types of CNs. While they share some fundamental properties like low density, biodegradability, biocompatibility, and low toxicity, they also possess unique differentiating characteristics such as morphology, rheology, aspect ratio, crystallinity, mechanical and optical properties. Therefore, numerous comparative studies have been conducted, and recently, various studies have reported the synergetic advantages resulting from combining CNF and CNC. In this review, we initiate by addressing the terminology used to describe combinations of these and other types of CNs, proposing "hybrid cellulose nanomaterials" (HCNs) as the standardized classifictation for these materials. Subsequently, we briefly cover aspects of properties-driven applications and the performance of CNs, from both an individual and comparative perspective. Next, we comprehensively examine the potential of HCN-based materials, highlighting their performance for various applications. In conclusion, HCNs have demonstraded remarkable success in diverse areas, such as food packaging, electronic devices, 3D printing, biomedical and other fields, resulting in materials with superior performance when compared to neat CNF or CNC. Therefore, HCNs exhibit great potential for the development of environmentally friendly materials with enhanced properties.

High-yield production of rod-like and spherical nanocellulose by controlled enzymatic hydrolysis of mechanically pretreated cellulose.

In this study, a simple and scalable mechanical pretreatment was evaluated as means of enhancing the accessibility of cellulose fibers, with the objective of improving the efficiency of enzymatic reactions for the production of cellulose nanoparticles (CNs). In addition, the effects of enzyme type (endoglucanase - EG, endoxylanase - EX, and a cellulase preparation - CB), composition ratio (0-200UEG:0-200UEX or EG, EX, and CB alone), and loading (0 U-200 U) were investigated in relation to CN yield, morphology, and properties. The combination of mechanical pretreatment and specific enzymatic hydrolysis conditions substantially improved CN production yield, reaching up to 83 %. The production of rod-like or spherical nanoparticles and their chemical composition were highly influenced by the enzyme type, composition ratio, and loading. However, these enzymatic conditions had minimal impact on the crystallinity index (approximately 80 %) and thermal stability (Tmax within 330-355 °C). Overall, these findings demonstrate that mechanical pretreatment followed by enzymatic hydrolysis under specific conditions is a suitable method to produce nanocellulose with high yield and adjustable properties such as purity, rod-like or spherical forms, high thermal stability, and high crystallinity. Therefore, this production approach shows promise in producing tailored CNs with the potential for superior performance in various advanced applications, including, but not limited to, wound dressings, drug delivery, thermoplastic composites, 3D (bio)printing, and smart packaging.

Exploring the action of endoglucanases on bleached eucalyptus kraft pulp as potential catalyst for isolation of cellulose nanocrystals.

Cellulose nanocrystals (CNCs) is a high-value and emerging bionanomaterial with an increasing number of applications. The action of endoglucanases (EGs) from fungal and bacterial sources belonging to three glycosyl hydrolase (GH) families were investigated on bleached eucalyptus kraft pulp as potential catalysts to prepare CNC. Fungal GH7EG was the most efficient in hydrolysis and fiber fragmentation without altering crystallinity and crystallite size. Fiber fragmentation promoted by fungal GH45EG was similar to that observed for GH7EG, although it released a smaller amount of sugar. Bacterial GH5EG resulted in very low hydrolysis yield and practically did not fragment the fibers, resulting in a hydrolysis residue with characteristics very similar to the initial material. GH45EG was the only EG that affected the crystallinity and crystallite size and also the only enzyme capable of isolating nanoparticles. The isolated nanoparticles had very narrow width distribution range of 6-10 nm and length distribution range of 400-600 nm. Supplementation of ß-glucosidase and conventional mechanical refining as a pretreatment did not improve the release of nanoparticles. Despite catalyzing the same biochemical reaction, different EGs displayed very distinct action during hydrolysis. The reported strong binding of GH45EG's CBM to the cellulose and the lack of increased accessibility of the enzyme to new substrate likely allowed continuous hydrolysis of the few fibers available, resulting in the isolation of cellulose nanoparticles.