CHITOSAN COMPOSITE MATERIALS FROM Calliptamus italicus L. AND THEIR SOME PROPERTIES

ABSTRACT

Chitin was extracted from “Calliptamus italicus L.”, an insect recognized as a significant source of chitin. Chitosan, derived from chitin, was isolated with a yield of 26.7%. The molecular weight and degree of deacetylation (DDA) of the obtained chitosan were determined through various analytical methods. The physical properties of the chitosan were characterized using X-ray diffraction (XRD) spectroscopy, infrared (IR) spectroscopy, viscometry, and elemental analysis.

АННОТАЦИЯ

Хитин был выделен из Calliptamus italicus L. — насекомого, признанного значительным источником хитина. Хитозан, полученный из хитина, был выделен с выходом 26,7%. Молекулярная масса и степень дезацетилирования (ДДА) полученного хитозана были определены с использованием различных аналитических методов. Физико-химические свойства хитозана исследованы с применением рентгеновской дифракции (XRD), инфракрасной (ИК) спектроскопии, вискозиметрии и элементного анализа.

Keywords: Calliptamus italicus L., chitin, chitosan, composite material, film, viscosity.

Ключевые слова: Calliptamus italicus L., хитин, хитозан, композиционный материал, пленка, вязкость.

Introduction

Nowadays, there is increasingly mounting interest and demand for biologically and environmentally friendly foodstuffs and food additives that are perceived as useful to human health. Meanwhile, much of the world's contemporary scientific research is aimed at resolving current global issues, like the increasing deficiency of food products and prevention and minimization of environmental pollution [1]. One of the significant reasons for these issues is the wastes produced by human activities. The most effective and best method to address these kinds of issues is to utilize the resources obtained from nature. In this regard, chitin—a protein-rich substance—is gaining more attention globally.

Chitin is mainly obtained from crustaceans, fungi, animal horns, and grasshoppers, bees, beetles, silkworms, and other insects [2–4]. Based on natural occurrence, chitin is the second most widespread biologically active polysaccharide after cellulose [5]. Due to the biological activity of its derivative, chitosan, technological applications involving its processing are incessantly expanding. Chitosan is utilized in medicine, pharmaceutical industry, and the food industry as a bioactive additive, and also in the form of various preparations such as gels, ointments, capsules, sols, and film materials. Most important among them are film materials. Due to the antimicrobial and antioxidant activities exhibited by chitosan films, they are employed for wound dressing of open wounds and as biodegradable substitutes for plastics for packaging of foods [6].

Obtaining of chitosan from insects is less rigorous than from crustaceans. Research has proved that the product of chitosan from insects is greater in amount and useful than that found from crustacean shells. Precisely, chitosan from insect origin—grasshoppers, caterpillars, silkworm cocoons proved to have more extensive water-absorption (hydrophilicity) levels of 594–795%, and lipids-binding ability of 275–645% than chitosan from crustaceans [7].

Figure 1. Traditional method for extracting chitosan from Calliptamus italicus L.

Insects are composed of several constituents, the bulk of which is 30–45% protein, 25–40% fat, 10–15% chitin, and traces of minerals and pigments [8]. Among these constituents, chitin is considered a precious biopolymer. Chitin and its derivative chitosan are mainly extracted from insects using chemical extraction methods. This process has been referred to as a conventional chemical process and considered to be an economical and simple procedure for the separation of chitosan with high yield, without any contaminants (Figure 1).

Materials and Methods

Isolation of Chitosan from Calliptamus italicus L. and Its Use in Composite Material Synthesis. Calliptamus italicus L., a locust species native to the territory of Uzbekistan, was selected as the raw material for chitosan extraction. The isolation of chitin from Calliptamus italicus L. was carried out by removing its various constituent components using chemical reagents.

Initially, 10 grams of dried Calliptamus italicus L. (steppe locust) was weighed. To ensure full submersion, the raw material was immersed in 100 mL of 96% ethanol at a 1:10 (w/v) ratio. For the demineralization step, 7% HCl solution was used. The sample was placed into a flask, and an amount of 7% HCl was added in a 1:10 (w/v) ratio. After acid treatment, the demineralized material was treated with 60 mL of 4% KOH solution and maintained at 70°C for 60 minutes to remove proteins.

The resulting chitin yield was 11.1% relative to the initial dry mass. To remove residual pigments, a depigmentation step was carried out using hydrogen peroxide (30%), potassium permanganate (5%), and sodium bicarbonate (4%) in a 1 g:10 mL ratio. Following depigmentation, the obtained chitosan displayed a white-gray coloration.

Determination of Degree of Deacetylation (DDA). The degree of deacetylation (DDA) of chitin and chitosan is a significant parameter that depends on the extraction method, reaction time, and alkali concentration. It significantly affects the chemical and biological activity of chitosan. Several methods for determining this indicator exist, including potentiometric titration, conductometric titration, acid-base titration, FTIR spectroscopy, and nitrogen content[7].

In the current study, the DDA of chitosan obtained from Calliptamus italicus L. was determined using CHNS elemental analysis. The DDA was determined to be 86.7%.

The molecular weight (Mw) of the chitosan derived from Calliptamus italicus L. was determined by the viscometric method to be 355 kDa. For the synthesis of chitosan-based composite materials, a 1% chitosan solution was prepared by dissolving it in 1% acetic acid. Glycerol was added as a plasticizer. Subsequently, zinc oxide (ZnO) was added to the chitosan solution at varying mass ratios (0.02 g, 0.03 g, and 0.05 g per 1 g of chitosan). The mixture was stirred using a magnetic stirrer at 300 rpm and 25°C for 6 hours in a sealed flask until complete dissolution was achieved.

Characterization of Chitosan and Its Composite Samples. For the identification of chitosan and its composite samples, FTIR analysis was carried out using a Fourier-transform infrared spectrometer (Bruker) in the spectral range of 4000–400 cm⁻¹, with ZnSe optics and a resolution of 0.5 cm⁻¹. To investigate the crystallinity and structural characteristics, X-ray diffraction (XRD) analysis was performed using a Rigaku MiniFlex-600 benchtop diffractometer. The measurements were conducted with CuKα radiation (λ = 0.15406 nm, 40 kV, 15 mA). Scanning was performed over a 5°–45° 2θ range for pure chitosan, and a 10°–45° range for the composite materials, at a scan rate of 3°/min and a step size of 0.05°.

All chemical reagents used in this study were purchased from ChemReagents.

Structural Characterization of Chitosan

To determine the degree of crystallinity of the chitosan structure derived from Calliptamus italicus L., XRD analysis was carried out.

a)                                                                                b)

 Figure 2. a) XRD analysis of chitosan extracted from crustaceans b) XRD of chitosan extracted from Calliptamus italicus L.

It was noted that the chitosan exhibited two broad peaks at 2θ = 9.56 and 20.21 (Figure 2b). The first peak was not as intense as the second, which verified the presence of Crystal I and Crystal II forms. This finding confirms that the chitosan chains possess a semi-crystalline orthorhombic structure [9–11]. In many studies, the characteristic peaks of chitosan observed in XRD analysis are generally found around 2θ = 10° and 20°, forming two distinct peaks (Figure 2a) [12]. According to researchers, the reason for the variation in these characteristic peaks may be related to the source of the extracted chitin.

Preparation of film materials based on chitosan

Film materials based on chitosan are gaining increasing attention due to their biodegradable nature and biological activities, including antioxidant, antimicrobial, and antibacterial properties. For the preparation of chitosan films, a 1% solution of chitosan (with a molecular weight of 355 kDa) was prepared in a 1% acetic acid solution.

Results Analysis

FTIR Spectroscopic Characterization of Chitosan and Its Film Derived from Calliptamus italicus L.

FTIR spectroscopy was conducted to study the structural and elemental composition of the chitosan extracted from in sects and the films derived from it.

a)

b)

Figure 3.. a) Chitosan b) Chitosan/ZnO/acetic acid composite IR spectroscopy

The results of the FTIR spectroscopy analysis of chitosan extracted from Calliptamus italicus L. revealed the presence of functional groups in the chitosan structure. In Figure a, the characteristic vibrational bands corresponding to -OH, -NH₂, and -CH₂ functional groups were observed. Specifically, the peaks at 3358 cm^⁻¹ correspond to the -OH group, 3295 cm^⁻¹ corresponds to -NH₂, 1647 cm^⁻¹ corresponds to the amine II group, 1583 cm^⁻¹ corresponds to the amine group, 1059 cm⁻¹ is associated with C-O, and 1027 cm^⁻¹ corresponds to the -NH(C=O) bond. However, slight shifts were observed, with the peak at 1647 cm^⁻¹ shifting to 1595 cm^⁻¹, and the peak at 1598 cm^⁻¹ shifting to 1515 cm^⁻¹, indicating broadening of the peaks[13]. When zinc oxide (ZnO) was added to the acetic acid solution of chitosan under specific conditions, the FTIR analysis of the resulting chitosan-zinc oxide composite film showed the formation of a zinc-ion (Zn²⁺) composite. As shown in Figure b, the FTIR spectrum of the composite film reveals that the characteristic signals of the chitosan-acetic acid film remained intact, while new signals corresponding to the zinc oxide composite material were also observed.

Conclusion

The degree of deacetylation of chitosan extracted from Calliptamus italicus L. was found to be 86%. Its molecular mass was determined to be 355 kDa by calculating its viscosity. During the study of this high-molecular-weight chitosan and the film material produced from it, it was confirmed through physical research methods that the material is a composite. The biodegradable properties of the film were studied in different environments, and the degradation process was found to be time-dependent. The results indicate that the chitosan obtained from Calliptamus italicus L. can be an environmentally friendly and biodegradable alternative, suitable for industrial-scale production of film materials.

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