Chitin nanocrystals prepared by oxidation of α-chitin using the O2/laccase/TEMPO system

Tunable Oxidized-Chitin Hydrogels with Customizable Mechanical Properties by Metal or Hydrogen Ion Exposure

This study focuses on the optimization of chitin oxidation in C6 to carboxylic acid and its use to obtain a hydrogel with tunable resistance. After the optimization, water-soluble crystalline β-chitin fibrils (β-chitOx) with a degree of functionalization of 10% were obtained. Diverse reaction conditions were also tested for α-chitin, which showed a lower reactivity and a slower reaction kinetic. After that, a set of hydrogels was synthesized from β-chitOx 1 wt.% at pH 9, inducing the gelation by sonication. These hydrogels were exposed to different environments, such as different amounts of Ca2+, Na+ or Mg2+ solutions, buffered environments such as pH 9, PBS, pH 5, and pH 1, and pure water. These hydrogels were characterized using rheology, XRPD, SEM, and FT-IR. The notable feature of these hydrogels is their ability to be strengthened through cation chelation, being metal cations or hydrogen ions, with a five- to tenfold increase in their storage modulus (G'). The ions were theorized to alter the hydrogen-bonding network of the polymer and intercalate in chitin's crystal structure along the a-axis. On the other hand, the hydrogel dissolved at pH 9 and pure water. These bio-based tunable hydrogels represent an intriguing material suitable for biomedical applications.

Adenosine Triphosphate/Chitin Whisker/Phenylboronic Acid-Modified Wool Fabrics with Enhanced Dyeability

Promoting the uptake of dyes is an important part of the sustainable processing of wool products. This study presents an effective modification approach to enhance the dyeability of wool fabric with adenosine triphosphate as an activator, 3-carboxyphenyl boronic acid as a ligand-binding agent, and chitin whisker as a couple agent. The structure and surface morphology of the as-prepared wool fabric was characterized in detail. Natural luteolin and acid red 1 were used to dye the modified wool fabric, and the effect of different dyeing parameters on dyeing properties was discussed. The results indicated that the modified wool gained better surface color depth (K/S) and uptake without additional agents than the untreated wool fabric. When the modified wool fabric was dyed at 45 °C with luteolin and at 60 °C with acid red 1, the dyeing processes of the two dyes on the modified wool fabrics followed the Langmuir isotherm and the pseudo-second-order kinetic model. Furthermore, the dyed modified wool fabrics possessed improved color fastness. Overall, this work offers a facile, effective, and sustainable way to improve the low-temperature dyeability of wool products.

Chitin nanofibers prepared by enzymatic hydrolysis: Characterization and application for Pickering emulsions

Chitin nanofibers (ChNFs) have a wide range of applications in numerous fields owing to their exceptional material properties and biological functionality. This research focused on producing ChNFs with diameters of 20-70 nm using chitinase and ultrasound from crayfish shells. The impact of enzymatic duration on ChNF yield and performance was investigated. Results revealed ChNFs forming a high aspect ratio network structure. Chitinase hydrolysis enhanced ChNF dispersion and yield while improving crystallinity and thermal stability without significantly altering their chemical structure. Enzymatically modified ChNF suspensions also exhibited stable rheological properties. Moreover, ChNFs showed good emulsification and emulsion stability in Pickering emulsion. The mechanism may be the effective adsorption of ChNFs at the oil-water interface, and the formation of a ChNF network in the continuous phase that prevents droplet coalescence. This study highlights that the potential of chitinase and ultrasound for the production of ChNFs and the utilization of crayfish shell waste.

Oxidized of chitosan with different molecular weights for potential antifungal and plant growth regulator applications

The application of Chitosan (CS) in drug delivery systems, plant growth promotion, antibacterial potentiality and plant defense is significantly limited by its inability to dissolve in neutral solutions. In this work, CS with different molecular weights (Mw) has been oxidized, yielding five kinds of oxidized chitosan (OCS 1-5) with solubilities in neutral solutions. The results obtained from Fourier Transform Infrared Spectroscopy clearly showed the successful oxidation of the hydroxyl group to form aldehyde and carboxyl groups. And the CS derivatives showed the wrinkled and lamellar structures on the surface of OCS. The results of antifungal activity against Fusarium graminearum showed that the OCS dissolved in 2 % (V/V) acetic acid exhibited better performance of almost complete inhibition of mycelial growth compared with CS at the concentration of 500 μg/mL. Among the five OCS, OCS-4 exhibited the best antifungal effect and had the lowest EC50 value of 581.68 μg/mL in samples. OCS-4 displayed superior promoting effect on seed germination with a germination potential of 62.2 % at a concentration of 3 g/L and a germination rate of 74.5 %. Additionally, the other four OCS also showed excellent antifungal activity with dose-dependent manners. These results indicated that the OCS had excellent antifungal potential in agricultural production.

Effect of Surface Functionality on the Rheological and Self-Assembly Properties of Chitin and Chitosan Nanocrystals and Use in Biopolymer Films

Chitin nanocrystals (ChNCs) are unique to all other bio-derived nanomaterials in one aspect: the inherent presence of a nitrogen moiety. By tuning the chemical functionality of this nanomaterial, and thus its charge and hydrogen bonding capacity, one can heavily impact its macroscopic properties such as its rheological and self-assembly characteristics. In this study, two types of ChNCs are made using acid hydrolysis (AH-ChNCs) and oxidative (OX-ChNCs) pathways, unto which deacetylation using a solvent-free procedure is utilized to create chitosan nanocrystals (ChsNCs) of varying degree of deacetylation (DDA). These nanocrystals were then studied for their rheological behavior and liquid crystalline ordering. It was found that with both deacetylation and carboxylation of ChNCs, viscosity continually increased with increasing concentrations from 2 to 8 wt %, contrary to AH-ChNC dispersions in the same range. Interestingly, increasing the amine content of ChNCs was not proportional to the storage modulus, where a peak saturation of amines provided the most stiffness. Conversely, while the introduction of carboxylation increased the elastic modulus of OX-ChNCs by an order of magnitude from that of AH-ChNCs, it was decreased by increasing DDA. Deacetylation and carboxylation both inhibited the formation of a chiral nematic phase. Finally, these series of nanocrystals were incorporated into biodegradable pectin-alginate films as a physical reinforcement, which showed increased tensile strength and Young's modulus values for the films incorporated with ChsNCs. Overall, this study is the first to investigate how surface functionalization of chitin-derived nanocrystals can affect their rheological and liquid crystalline properties and how it augments pectin/alginate films as a physical reinforcement nanofiller.

Nano-chitin: Preparation strategies and food biopolymer film reinforcement and applications

Current trends in food packaging systems are toward biodegradable polymer materials, especially the food biopolymer films made from polysaccharides and proteins, but they are limited by mechanical strength and barrier properties. Nano-chitin has great economic value as a highly efficient functional and reinforcing material. The combination of nano-chitin and food biopolymers offers good opportunities to prepare biodegradable packaging films with enhanced physicochemical and functional properties. This review aims to give the latest advances in nano-chitin preparation strategies and its uses in food biopolymer film reinforcement and applications. The first part systematically introduces various preparation methods for nano-chitin, including chitin nanofibers (ChNFs) and chitin nanocrystals (ChNCs). The nano-chitin reinforced biodegradable films based on food biopolymers, such as polysaccharides and proteins, are described in the second part. The last part provides an overview of the current applications of nano-chitin reinforced food biopolymer films in the food industry.

Nanochitin and Nanochitosan: Chitin Nanostructure Engineering with Multiscale Properties for Biomedical and Environmental Applications

Nanochitin and nanochitosan (with random-copolymer-based multiscale architectures of glucosamine and N-acetylglucosamine units) have recently attracted immense attention for the development of green, sustainable, and advanced functional materials. Nanochitin and nanochitosan are multiscale materials from small oligomers, rod-shaped nanocrystals, longer nanofibers, to hierarchical assemblies of nanofibers. Various physical properties of chitin and chitosan depend on their molecular- and nanostructures; translational research has utilized them for a wide range of applications (biomedical, industrial, environmental, and so on). Instead of reviewing the entire extensive literature on chitin and chitosan, here, recent developments in multiscale-dependent material properties and their applications are highlighted; immune, medical, reinforcing, adhesive, green electrochemical materials, biological scaffolds, and sustainable food packaging are discussed considering the size, shape, and assembly of chitin nanostructures. In summary, new perspectives for the development of sustainable advanced functional materials based on nanochitin and nanochitosan by understanding and engineering their multiscale properties are described.

Influence of glucan on physicochemical and rheology properties of chitin nanofibers prepared from Shiitake stipes

Procedures for chitin nanofibers extraction from mushroom significantly modify their structure and physicochemical properties, through disintegration and surface oxidation of glucan residue, as well as surface deacetylation of chitin. Here, four kinds of chitin-glucan nanofibers (CGNF) were isolated form Shiitake stipes via different alkali treatment conditions, wherein glucan content ranged from 6.4 % to 46.8 %. Observations with transmission electron microscopy showed that CGNFs possessed average widths with 5.1 ± 1.2 to 7.1 ± 1.5 nm. The glucan showed a negative effect on the crystal index and thermal stability of CGNFs. A strong positive correlation was observed between glucan residues and zeta potential value. The phenomenon about the increase of viscosity, yield stress and elastic modulus upon glucan decrease was discussed. Overall, the residual glucan offers fungi-derived chitin nanomaterials a diversity of material properties and tuning its content is a feasible approach for customize nano chitin fibers used in nutraceutical and food industry.

Nanochitin: Chemistry, Structure, Assembly, and Applications

Chitin, a fascinating biopolymer found in living organisms, fulfills current demands of availability, sustainability, biocompatibility, biodegradability, functionality, and renewability. A feature of chitin is its ability to structure into hierarchical assemblies, spanning the nano- and macroscales, imparting toughness and resistance (chemical, biological, among others) to multicomponent materials as well as adding adaptability, tunability, and versatility. Retaining the inherent structural characteristics of chitin and its colloidal features in dispersed media has been central to its use, considering it as a building block for the construction of emerging materials. Top-down chitin designs have been reported and differentiate from the traditional molecular-level, bottom-up synthesis and assembly for material development. Such topics are the focus of this Review, which also covers the origins and biological characteristics of chitin and their influence on the morphological and physical-chemical properties. We discuss recent achievements in the isolation, deconstruction, and fractionation of chitin nanostructures of varying axial aspects (nanofibrils and nanorods) along with methods for their modification and assembly into functional materials. We highlight the role of nanochitin in its native architecture and as a component of materials subjected to multiscale interactions, leading to highly dynamic and functional structures. We introduce the most recent advances in the applications of nanochitin-derived materials and industrialization efforts, following green manufacturing principles. Finally, we offer a critical perspective about the adoption of nanochitin in the context of advanced, sustainable materials.

Contributions of Women in Recent Research on Biopolymer Science

Nowadays, biopolymers are playing a fundamental role in our society because of the environmental issues and concerns associated with synthetic polymers. The aim of this Special Issue entitled ‘Women in Polymer Science and Technology: Biopolymers’ is highlighting the work designed and developed by women on biopolymer science and technology. In this context, this short review aims to provide an introduction to this Special Issue by highlighting some recent contributions of women around the world on the particular topic of biopolymer science and technology during the last 20 years. In the first place, it highlights a selection of important works performed on a number of well-studied natural polymers, namely, agar, chitin, chitosan, cellulose, and collagen. Secondly, it gives an insight into the discovery of new polysaccharides and enzymes that have a role in their synthesis and in their degradation. These contributions will be paving the way for the next generation of female and male scientists on this topic.

Preparation, Characterization and Gelation of a Fungal Nano Chitin Derived from Hericium erinaceus Residue

Nano chitin is a promising biocompatible material with wide applications. In this work, a fungal-derived nano chitin was prepared from Hericium erinaceus residue via mineral/protein purification and subsequent TEMPO-mediated oxidation. The structure, dispersity, and gelation ability of the prepared fungal nano chitin were studied. The results showed that the average length and width of the prepared fungal nano chitin were 336.6 nm and 6.4 nm, respectively, and the aspect ratio exceeded 50:1. The nano chitin retained the basic structure of chitin, while the crystallization index was improved. In addition, the dispersity of the nano chitin in aqueous media was evaluated by the effective diameter, and the polydispersion index was mainly affected by pH and ionic strength. Under acetic acid "gas phase coagulation", the prepared nano chitin dispersions with mass concentrations of 0.2, 0.4, 0.6, and 0.8% were converted into gels by enhanced hydrogen bond crosslinking between nano chitins.

Chitin Nanocrystals: Environmentally Friendly Materials for the Development of Bioactive Films

Biobased nanomaterials have gained growing interest in recent years for the sustainable development of composite films and coatings, providing new opportunities and high-performance products. In particular, chitin and cellulose nanocrystals offer an attractive combination of properties, including a rod shape, dispersibility, outstanding surface properties, and mechanical and barrier properties, which make these nanomaterials excellent candidates for sustainable reinforcing materials. Until now, most of the research has been focused on cellulose nanomaterials; however, in the last few years, chitin nanocrystals (ChNCs) have gained more interest, especially for biomedical applications. Due to their biological properties, such as high biocompatibility, biodegradability, and antibacterial and antioxidant properties, as well as their superior adhesive properties and promotion of cell proliferation, chitin nanocrystals have emerged as valuable components of composite biomaterials and bioactive materials. This review attempts to provide an overview of the use of chitin nanocrystals for the development of bioactive composite films in biomedical and packaging systems.

Chiral Nematic Cellulose Nanocrystal Films Cooperated with Amino Acids for Tunable Optical Properties

The exploration of functional materials relies greatly on the understanding of material structures and nanotechnologies. In the present work, chiral nematic cellulose nanocrystal (CNC) films were prepared by incorporation with four types of amino acids (AAs, glycine, histidine, phenylalanine, and serine) via evaporation-induced self-assembly. The films present ideal iridescence and birefringence that can be tuned by the amount of AAs added. The intercalation of AAs enlarged the pitch values, contributing to the red-shift trend of the reflective wavelength. Among the AAs, serine presented the most compatible intercalation into cellulose crystals. Interestingly, histidine and phenylalanine composite films showed high shielding capabilities of UV light in diverse wavelength regions, exhibiting multi-optical functions. The sustainable preparation of chiral nematic CNC films may provide new strategies for materials production from biocompatible lignocellulose.

Deconstruction and Reassembly of Renewable Polymers and Biocolloids into Next Generation Structured Materials

This review considers the most recent developments in supramolecular and supraparticle structures obtained from natural, renewable biopolymers as well as their disassembly and reassembly into engineered materials. We introduce the main interactions that control bottom-up synthesis and top-down design at different length scales, highlighting the promise of natural biopolymers and associated building blocks. The latter have become main actors in the recent surge of the scientific and patent literature related to the subject. Such developments make prominent use of multicomponent and hierarchical polymeric assemblies and structures that contain polysaccharides (cellulose, chitin, and others), polyphenols (lignins, tannins), and proteins (soy, whey, silk, and other proteins). We offer a comprehensive discussion about the interactions that exist in their native architectures (including multicomponent and composite forms), the chemical modification of polysaccharides and their deconstruction into high axial aspect nanofibers and nanorods. We reflect on the availability and suitability of the latter types of building blocks to enable superstructures and colloidal associations. As far as processing, we describe the most relevant transitions, from the solution to the gel state and the routes that can be used to arrive to consolidated materials with prescribed properties. We highlight the implementation of supramolecular and superstructures in different technological fields that exploit the synergies exhibited by renewable polymers and biocolloids integrated in structured materials.

The Food-Materials Nexus: Next Generation Bioplastics and Advanced Materials from Agri-Food Residues

The most recent strategies available for upcycling agri-food losses and waste (FLW) into functional bioplastics and advanced materials are reviewed and the valorization of food residuals are put in perspective, adding to the water-food-energy nexus. Low value or underutilized biomass, biocolloids, water-soluble biopolymers, polymerizable monomers, and nutrients are introduced as feasible building blocks for biotechnological conversion into bioplastics. The latter are demonstrated for their incorporation in multifunctional packaging, biomedical devices, sensors, actuators, and energy conversion and storage devices, contributing to the valorization efforts within the future circular bioeconomy. Strategies are introduced to effectively synthesize, deconstruct and reassemble or engineer FLW-derived monomeric, polymeric, and colloidal building blocks. Multifunctional bioplastics are introduced considering the structural, chemical, physical as well as the accessibility of FLW precursors. Processing techniques are analyzed within the fields of polymer chemistry and physics. The prospects of FLW streams and biomass surplus, considering their availability, interactions with water and thermal stability, are critically discussed in a near-future scenario that is expected to lead to next-generation bioplastics and advanced materials.

Chitin and chitosan on the nanoscale

In a matter of decades, nanomaterials from biomass, exemplified by nanocellulose, have rapidly transitioned from once being a subject of curiosity to an area of fervent research and development, now reaching the stages of commercialization and industrial relevance. Nanoscale chitin and chitosan, on the other hand, have only recently begun to raise interest. Attractive features such as excellent biocompatibility, antibacterial activity, immunogenicity, as well as the tuneable handles of their acetylamide (chitin) or primary amino (chitosan) functionalities indeed display promise in areas such as biomedical devices, catalysis, therapeutics, and more. Herein, we review recent progress in the fabrication and development of these bio-nanomaterials, describe in detail their properties, and discuss the initial successes in their applications. Comparisons are made to the dominant nanocelluose to highlight some of the inherent advantages that nanochitin and nanochitosan may possess in similar application.

Optimized Hierarchical Structure and Chemical Gradients Promote the Biomechanical Functions of the Spike of Mantis Shrimps

The tail spike of the mantis shrimp is the appendage for counteracting the enemy from behind. Here, we investigate the correlations between the chemical compositions, the microstructures, and the mechanical properties of the spike. We find that the spike is a hollow beam with a varying cross section along the length. The cross section comprises four different layers with distinct features of microstructures and chemical compositions. The local mechanical properties of these layers correlate well with the microstructures and chemical compositions, a combination of which effectively restricts the crack propagation while maximizing the release of strain energy during deformation. Finite element analysis and mechanics modeling demonstrate that the optimized structure of the spike confines the mechanical damage in the region near the tip and prevents catastrophic breakage at the base. Furthermore, we use a 3D printing technique to fabricate multiple hollow cylindrical samples consisting of biomimetic microstructures of the spike and confirm that the combination of the Bouligand structure with radially oriented parallel sheets greatly improves the toughness and strength during compression tests. The multiscale design strategy of the spike revealed here is expected to be of great interest for the development of novel bioinspired materials.

Synthesis and effects of the selective oxidation of chitosan in induced disease resistance against Botrytis cinerea

Plant fungal diseases can lead to yield reduction and quality degradation in crops, which usually cause serious economic losses. Additionally, chemical fungicides used in the prevention and control of plant diseases are increasingly restricted due to resistance development and high toxicity. Therefore, biogenic fungicides such as chitosan with low toxicity and good biocompatibility are receiving increasing attention. This study found that the acid swelling chitosan pretreatment method can accelerate the rate of the specific oxidation of chitosan catalyzed by the TEMPO-NaBr-NaOCl system. This study proved that OCTS induces plant disease resistance, and the control efficiencies achieved in protection and treatment experiments against Botrytis cinerea were 80.6 % and 83.4 %, respectively, at 400 μg/mL OCTS. In addition, OCTS can promote plant growth and enhance plant defense enzyme activities. This research has realized a forward-looking exploration of the application of OCTS in the agricultural field.

Chitin nanocrystals based complex fluids: A green nanotechnology

Chitin biopolymer has received significant attention recently by many industries as a green technology. Nanotechnology has been used to make chitin nanocrystals (ChiNCs) that are rod-shaped natural nanomaterials with nanoscale size. Owing to the unique features such as biodegradability, biocompatibility, renewability, rod-shape, and excellent surface and interfacial, physiochemical, and thermo-mechanical properties; ChiNCs have been green and attractive products with wide applications specifically in medical and pharmaceutical, food and packaging, cosmetic, electrical, and electronic, and also in the oil and gas industry. This review aims to give a comprehensive and applied insight into ChiNCs technology. It starts with reviewing different sources of chitin and their extraction methods followed by the characterization of ChiNCs. Furthermore, a detailed investigation into various complex fluids (dispersions, emulsions, foams, and gels) stabilized by ChiNCs and their characterisation have been thoroughly deliberated. Finally, the current status including ground-breaking applications, untapped investigations, and future prospective have been presented.

A review on native well-preserved chitin nanofibrils for materials of high mechanical performance

Novel chitin nanofibrils (ChNF) demonstrate excellent mechanical properties due to a long and extended polymer conformation. The current study highlights the importance of preserving ChNFs for stronger nanomaterials. Various chitin sources - crab, lobster, shrimp, squid pen, mushrooms, and insects have been reviewed. We have discussed preparation protocols and the physical properties of ChNF and presented the mechanical performance of nanomaterials. ChNF close to the native state uses fewer chemicals for treatment and shows a higher molar mass, degree of acetylation, crystallinity index, micrometer length, and a smaller diameter (3 nm), making them cheap, eco-friendly, and competitive to cellulose or synthetic fibrils. A highly acetylated or partially deacetylated ChNF forms a stable colloidal suspension, and it is possible to prepare from it strong films, hydrogels, aerogels, foams, polymer matrix nanocomposites, and microfibers. Moreover, it is possible to regenerate, functionalize, or cross-link the ChNFs to improve nanomaterials' mechanical performance. The preparation protocols remain the key to these achievements. However, the chemical techniques are not friendly ecologically and may hydrolytically degrade the chitin. The biological processes using enzymes or microorganisms are much better but still inefficient. Besides, the processing time limits the rapid preparation of the fibrils in the long-term perspective.

Characterization of TEMPO-oxidized chitin nanofibers with various oxidation times and its application as an enzyme immobilization support

Chitin nanofibers have recently received increased attention and are considered to be a promising material for a wide range of applications because of their excellent characteristics. In this study, 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO)-oxidized chitin nanofibers (CNFs) with various oxidation times were prepared and characterized. CNFs with different oxidation times were then utilized for enzyme immobilization, using chymotrypsin as a model enzyme. The effects of oxidation time on enzyme immobilization were explored. Results showed characteristics of chitin nanofibers can be controlled by adjusting oxidation time. CNFs treated with TEMPO for 360 min showed the lowest crystallinity (79.13 ± 1.43%), the shortest length (241.70 ± 74.61 nm), the largest width (12.67 ± 3.43 nm), and the highest transmittance (73.01% at 800 nm). The activity of immobilized enzymes and enzyme loading showed good correlation to the carboxylate content of CNFs. The enzyme efficiency based on CNFs and the content of carboxylate groups peaked at the oxidization time of 60 min. When the additional amount of chymotrypsins (CTs) was 500 or 2000 mg/g carrier, the highest loading amount of CTs was 307.17 ± 4.08 or 726.82 ± 12.05 mg/g carrier, respectively.

Rate-Limited Reaction in TEMPO/Laccase/O2 Oxidation of Cellulose

The environment-friendly oxidation of cellulose by the 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO)/laccase/O₂ system is an alternative route with huge potential to prepare cellulose nanofibers. It is found that the concentration of TEMPO significantly affects the oxidation efficiency. An effective method for improving the oxidation effect is to increase the TEMPO concentration and prolong the oxidation time. To clarify the rate-limited step of TEMPO/laccase/O₂ oxidation of cellulose, the academically accepted oxidation process is divided into individual pathways. A series of experiments is conducted with laccase and the three forms of organocatalyst (TEMPO, oxoammonium (TEMPO+), and hydroxylamine (TEMPOH)) to simulate individual reactions and calculate the reaction rates. The concentrations of TEMPO and oxoammonium are monitored by EPR spectroscopy. The oxidation rate of TEMPO by laccase varies at different pH conditions, and laccase activity is much higher at pH 4.5. Other reactions without laccase involved express a higher reaction rate when the pH value increased. TEMPO is mainly regenerated through a comproportionation reaction between oxoammonium and hydroxylamine. The acceleration of TEMPO regeneration by laccase is not obvious. The results indicate that the rate-limited reaction in TEMPO/laccase/O₂ oxidation is cellulose oxidation by TEMPO+.

From Cellulose to Cellulose Nanofibrils-A Comprehensive Review of the Preparation and Modification of Cellulose Nanofibrils

This review summarizes the preparation methods of cellulose nanofibrils (CNFs) and the progress in the research pertaining to their surface modification. Moreover, the preparation and surface modification of nanocellulose were comprehensively introduced based on the existing literature. The review focuses on the mechanical treatment of cellulose, the surface modification of fibrillated fibers during pretreatment, the surface modification of nanocellulose and the modification of CNFs and their functional application. In the past five years, research on cellulose nanofibrils has progressed with developments in nanomaterials research technology. The number of papers on nanocellulose alone has increased by six times. However, owing to its high energy consumption, high cost and challenging industrial production, the applications of nanocellulose remain limited. In addition, although nanofibrils exhibit strong biocompatibility and barrier and mechanical properties, their high hydrophilicity limits their practical application. Current research on cellulose nanofibrils has mainly focused on the industrial production of CNFs, their pretreatment and functional modification and their compatibility with other biomass materials. In the future, with the rapid development of modern science and technology, the demand for biodegradable biomass materials will continue to increase. Furthermore, research on bio-based nanomaterials is expected to advance in the direction of functionalization and popularization.

Preparation and surface modification of crab nanochitin for organogels based on thiol-ene click cross-linking

Incompatibility of chitin nanomaterials with organic solvents is challenging in the design of the desirable organogels. The long hydrocarbon chains were covalently grafted on the surface of nanochitins, with the attachment of reactive allyl groups and improved dispersion in organic solvents. The reactive thiol groups of poly (ethylene glycol) were introduced into the allyl-nanochitin suspensions to produce the organogels by the thiol-ene click reaction. Attributed to the UV-induced cross-linking between the soft segments of thiolated-PEG and the allyl-nanochitin, the stable organogels with the storage modulus higher than the loss modulus by one order of magnitude were obtained, exhibiting the significant phase transition and mechanical enhancement on the rheological behavior. The combination of crystalline allyl-nanochitin and polymeric chains played a crucial role in the construction of the micro-network, attributing to the stability and mechanical strength of the organogels.

Comparison of cast films and hydrogels based on chitin nanofibers prepared using TEMPO/NaBr/NaClO and TEMPO/NaClO/NaClO2 systems

Neutral TEMPO/NaClO/NaClO₂ (TNN) oxidation, with NaClO₂ as the primary oxidant under aqueous conditions at pH 6.8 was applied to selectively oxidize surface C6 primary hydroxyl groups of α-chitin to carboxylate groups. When 0.1 mmol TEMPO, 1 mmol NaClO and 20 mmol NaClO₂ were added to 1 g α-chitin, the yield of water-insoluble oxidized chitin was 91.93 %, and the carboxylate content was 0.695 mmol/g. The TNN oxidized chitin (TNN-Ch) was mostly converted to individual nanofibrils by mechanical disintegration in water, with mostly widths of 20-24 nm and average lengths of 1 μm. Compared to chitin nanofibers produced by TEMPO/NaBr/NaClO system (TBN-ChNs), with average widths of 16.67 ± 7.9 nm and average lengths of 770 ± 170 nm, TNN-ChNs were wider, longer and had a higher aspect ratio; its films and hydrogels also showed better mechanical properties, which indicated the size effect on the nanofiber-based materials resulted from different oxidation process.

Nanomaterials Derived from Fungal Sources-Is It the New Hype?

Greener alternatives to synthetic polymers are constantly being investigated and sought after. Chitin is a natural polysaccharide that gives structural support to crustacean shells, insect exoskeletons, and fungal cell walls. Like cellulose, chitin resides in nanosized structural elements that can be isolated as nanofibers and nanocrystals by various top-down approaches, targeted at disintegrating the native construct. Chitin has, however, been largely overshadowed by cellulose when discussing the materials aspects of the nanosized components. This Perspective presents a thorough overview of chitin-related materials research with an analytical focus on nanocomposites and nanopapers. The red line running through the text emphasizes the use of fungal chitin that represents several advantages over the more popular crustacean sources, particularly in terms of nanofiber isolation from the native matrix. In addition, many β-glucans are preserved in chitin upon its isolation from the fungal matrix, enabling new horizons for various engineering solutions.

Applications of Microbial Laccases: Patent Review of the Past Decade (2009–2019)

There is a high number of well characterized, commercially available laccases with different redox potentials and low substrate specificity, which in turn makes them attractive for a vast array of biotechnological applications. Laccases operate as batteries, storing electrons from individual substrate oxidation reactions to reduce molecular oxygen, releasing water as the only by-product. Due to society’s increasing environmental awareness and the global intensification of bio-based economies, the biotechnological industry is also expanding. Enzymes such as laccases are seen as a better alternative for use in the wood, paper, textile, and food industries, and they are being applied as biocatalysts, biosensors, and biofuel cells. Almost 140 years from the first description of laccase, industrial implementations of these enzymes still remain scarce in comparison to their potential, which is mostly due to high production costs and the limited control of the enzymatic reaction side product(s). This review summarizes the laccase applications in the last decade, focusing on the published patents during this period.