Effect of purification method of β-chitin from squid pen on the properties of β-chitin nanofibers

Cryomilling-assisted high purity β-chitin extraction from Uroteuthis edulis pens

We report on the extraction of β-chitin from pens (or Gladius) of Uroteuthis edulis, a squid species prevalent in the Pacific coastal regions of East Asia. In particular, we employ cryogenic mechanical grinding (or cryomilling) as a pre-treatment process for the raw squid pens. We show that the cryomilling step enables an effective pulverization of the raw materials, which facilitates the removal of protein residues allowing the extraction of high-purity β-chitin with a high acetylation degree (∼97 %) and crystallinity (∼82 %). We also demonstrate that the Uroteuthis edulis extract β-chitin affords a free-standing film with excellent optical transmittance and mechanical properties.

Multifunctional bilayer membranes composed of poly(lactic acid), beta-chitin whiskers and silver nanoparticles for wound dressing applications

Nanomaterial-based wound dressings have been extensively studied for the treatment of both minor and life-threatening tissue injuries. These wound dressings must possess several crucial characteristics, such as tissue compatibility, non-toxicity, appropriate biodegradability to facilitate wound healing, effective antibacterial activity to prevent infection, and adequate physical and mechanical strength to withstand repetitive dynamic forces that could potentially disrupt the healing process. Nevertheless, the development of nanostructured wound dressings that incorporate various functional micro- and nanomaterials in distinct architectures, each serving specific purposes, presents significant challenges. In this study, we successfully developed a novel multifunctional wound dressing based on poly(lactic acid) (PLA) fibrous membranes produced by solution-blow spinning (SBS) and electrospinning. The PLA-based membranes underwent surface modifications aimed at tailoring their properties for utilization as effective wound dressing platforms. Initially, beta-chitin whiskers were deposited onto the membrane surface through filtration, imparting hydrophilic character. Afterward, silver nanoparticles (AgNPs) were incorporated onto the beta-chitin layer using a spray deposition method, resulting in platforms with antimicrobial properties against both Staphylococcus aureus and Escherichia coli. Cytotoxicity studies demonstrated the biocompatibility of the membranes with the neonatal human dermal fibroblast (HDFn) cell line. Moreover, bilayer membranes exhibited a high surface area and porosity (> 80%), remarkable stability in aqueous media, and favorable mechanical properties, making them promising candidates for application as multifunctional wound dressings.

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.

Environment-friendly utilization of squid pen with water: Production of β-chitin nanofibers and peptides for lowering blood pressure

Chitin, an abundant biopolymer on Earth, represents a resource for sustainable functional materials. However, traditional β-chitin production methods involve alkaline treatment at approximately 90 °C for its separation from the protein, thus not suitable as a functional peptide, as it is mixed with an alkaline aqueous solution. This study examined the conversion of squid pen into solid β-chitin and water-soluble peptides using only water at temperatures of 150-250 °C for 30-120 min. Solid β-chitin was converted to its nanofiber form and the physicochemical properties of the β-chitin nanofibers were almost the same as those produced by the traditional method. Because this method uses only water, the protein in the squid pen may also be a functional peptide for lowering blood pressure, by inhibiting the Angiotensin-1 converting enzyme. High-temperature water treatment is a promising environment-friendly technique for complete utilization of squid pen components, including β-chitin and protein.

Valorization of food waste to produce intelligent nanofibrous β-chitin films

The efficient use of waste from food processing industry is one of the innovative approaches within sustainable development, because it can be transferred into added value products, which could improve economic, energetic and environmental sectors. In this context, the squid pen waste from seafood industry was used as raw material to obtain nanofibrous β-chitin films. In order to extend functionality of obtained films, elderberry extract obtained from biomass was added at different concentrations. The tensile strength of chitin-elderberry extract films was improved by 52%, elongation at break by 153% and water vapor barrier by 65%. The obtained material showed distinct color change when subjected to acidic or basic solutions. It was proven by CIELab color analysis that all color changes could be easily perceived visually. In addition, the obtained nanofibrous film was successfully used to monitor the freshness of Hake fish. Namely, when the film was introduced in a package that contained fresh fish, its color was efficiently changed within the time during the storage at 4 °C. The obtained results demonstrated that food processing waste could be efficiently valorized, and could give sustainable food package design as a spoilage indicator of high protein food.

Utilization of Marine Waste to Obtain β-Chitin Nanofibers and Films from Giant Humboldt Squid Dosidicus gigas

β-chitin was isolated from marine waste, giant Humboldt squid Dosidicus gigas, and further converted to nanofibers by use of a collider machine under acidic conditions (pH 3). The FTIR, TGA, and NMR analysis confirmed the efficient extraction of β-chitin. The SEM, TEM, and XRD characterization results verified that β-chitin crystalline structure were maintained after mechanical treatment. The mean particle size of β-chitin nanofibers was in the range between 10 and 15 nm, according to the TEM analysis. In addition, the β-chitin nanofibers were converted into films by the simple solvent-casting and drying process at 60 °C. The obtained films had high lightness, which was evidenced by the CIELAB color test. Moreover, the films showed the medium swelling degree (250-290%) in aqueous solutions of different pH and good mechanical resistance in the range between 4 and 17 MPa, depending on film thickness. The results obtained in this work show that marine waste can be efficiently converted to biomaterial by use of mild extractive conditions and simple mechanical treatment, offering great potential for the future development of sustainable multifunctional materials for various industrial applications such as food packaging, agriculture, and/or wound dressing.

Enhancing Saltiness Perception Using Chitin Nanomaterials

In the present study, we prepared and characterized chitin nanomaterials with different diameters, lengths, and degree of deacetylation (DD), and investigated their capability for enhancing saltiness perception. Chitin was isolated from squid pens and transformed into chitin nanofiber (CNF), deacetylated chitin nanofiber (DACNF), and chitin nanocrystal (CNC) by ultrasonication, alkali treatment followed by ultrasonication and acid hydrolysis, respectively. The diameters of CNF, CNC and DACNF were 17.24 nm, 16.05 nm and 15.01 nm while the lengths were 1725.05 nm, 116.91 nm, and 1806.60 nm, respectively. The aspect ratios of CNF and DACNF were much higher than that of CNC. The crystalline indices of CNF and CNC were lower than that of original β-chitin, suggesting that ultrasonication and acid hydrolysis might change the molecular arrangement in crystalline region of chitin. The zeta-potentials were between 19.73 nV and 30.08 mV of chitin nanomaterials in distilled water. Concentrations of chitin nanomaterials (40–74 μg/mL) showed minimal effect on zeta-potential, whereas increasing the level of NaCl reduced the zeta-potential of solution. Moreover, NaCl solution (0.3%) with chitin nanomaterials addition produced significant higher saltiness perception than that of solution with NaCl alone. Therefore, chitin nanomaterials may be promising saltiness enhancers in the food industry.

Preparation of β-chitin nanofiber aerogels by lyophilization

In this study, chitin nanofiber dispersions prepared in neutral and acidic pH conditions were lyophilized to produce aerogels. The effects of the freezing speed of the nanofiber dispersions and the dispersibility of the chitin nanofiber were studied. The characteristics of the aerogels were studied using scanning electron microscopy, relative surface area measurements, and compression tests. The repulsion forces of the chitin nanofiber in acidic conditions were effective in the formation of a more uniform microstructure during water solidification, resulting in aerogels with a high mechanical strength. The aerogel made from the chitin nanofiber dispersion prepared in neutral conditions was influenced by ice crystal growth during freezing, resulting in a nonuniform structure. In contrast, the surface area of the aerogel in neutral conditions interestingly remained unchanged compared to that of the original powder, which was due to the morphological transformation.

Development of biomineralization-inspired hybrids based on β-chitin and zinc hydroxide carbonate and their conversion into zinc oxide thin films

Hybrid thin films based on an environmentally friendly biopolymer, β-chitin and zinc hydroxide carbonate were developed through a biomineralization-inspired approach.

Systematic dynamic viscoelasticity measurements for chitin nanofibers prepared with various concentrations, disintegration times, acidities, and crystalline structures

Dynamic viscoelasticities were measured for chitin nanofiber (ChNF) dispersions prepared with various concentrations, disintegration times, acidities, and crystalline structures. The 0.05w/v% dispersions of pH neutral ChNFs continuously exhibited elastic behavior. The 0.05w/v% dispersions of acidified ChNFs, on the other hand, transitioned from a colloidal dispersion to a critical gel and then exhibited elastic behavior with increasing ChNF concentration. A double-logarithmic chart of the concentration vs. the storage modulus was prepared and indicated the fractal dimension and the nanostructure in the dispersion. The results determined that the neutral α- and β-ChNFs were dispersed but showed some remaining aggregations and that the acidified β-ChNFs were completely individualized. In addition, the α-chitin steadily disintegrated with increasing disintegration time, and the aspect ratio of the β-chitin decreased as a result of the exscessive disintegration. The storage moduli of the ChNFs were greater than those of chitin solutions, nanorods, and nanowhiskers with the same solids concentrations.

Effect of acidity on the physicochemical properties of α- and β-chitin nanofibers

We have investigated whether acidity can be used to control the physicochemical properties of chitin nanofibers (ChNFs). In this study, we define acidity as the molar ratio of dissociated protons from the acid to the amino groups in the raw chitin powder. The effect of acidity on the physicochemical properties of α- and β-ChNFs was compared. The transmittance and viscosity of the β-ChNFs drastically and continuously increased with increasing acidity, while those of the α-ChNFs were not affected by acidity. These differences are because of the higher ability for cationization based on the more flexible crystal structure of β-chitin than α-chitin. In addition, the effect of the acid species on the transmittance of β-ChNFs was investigated. The transmittance of β-ChNFs can be expressed by the acidity regardless of the acid species, such as hydrochloric acid, phosphoric acid, and acetic acid. These results indicate that the acidity defined in this work is an effective parameter to define and control the physicochemical properties of ChNFs.