Obtaining chitin, chitosan and their melanin complexes from insects

Efficient and green extraction of chitin from Hermetia illucens using deep eutectic solvents and its application for rapid hemostasis

Hermetia illucens, with a short growth cycle, is promising as a valuable source of chitin. However, the optimal method for extracting chitin from this insect and its application for hemostasis has not been addressed. This work employed an environmentally friendly choline chloride-lactic acid deep eutectic solvent technology to extract chitin effectively from the Hermetia illucens pupae shells, realizing one-step removal of inorganic salts and proteins. The extraction process was optimized through the response surface methodology, which identified the optimal temperature (92 °C), time (5.6 h), and liquid-solid ratio (20 mL/g) as the conditions that yielded the highest chitin yield (28.40 %) and the highest purity (96.93 %). The structural characterization of the extracted chitin revealed an α-type structure with favorable thermal stability. Furthermore, by regulating the degree of deacetylation, we optimized the degree of protonation of chitin for producing a series of chitosan (Cts), thereby enabling the production of Cts2 with excellent in vitro hemostatic properties. The superior hemostatic performance of Cts2 can be attributed to significantly superior platelet adhesion, achieved preferred adsorption of fibrinogen, and improved blood coagulation. This work provides a theoretical basis for the efficient extraction and high-value application of chitin from Hermetia illucens.

Insect chitosan derived from Hermetia illucens larvae suppresses adipogenic signaling and promotes the restoration of gut microbiome balance

Chitosan, the deacetylated form of chitin, is considered a valuable source of compounds in the feed and food industries. However, the impact of Hermetia illucens larvae chitosan (HCS) with specific physicochemical characteristics on obesity mediated by lipid accumulation and microbiome dysbiosis has not been fully elucidated. We purified HCS with a low molecular weight (84 kDa), low crystallinity, and a high deacetylation rate, characterizing it through several analytical techniques, including gel permeation chromatography, FT-IR, 1H NMR, FE-SEM, and XRD analysis. HCS effectively inhibited the differentiation of 3T3-L1 preadipocytes by suppressing the production of reactive oxygen species. The adipogenic signaling of preadipocytes, mediated by the phosphorylation of mTOR and PPARγ, which are essential for the expression of fatty acid synthase, was attenuated by HCS. In mouse models fed high-fat diets, the oral administration of HCS prevented changes in white adipose tissue and liver weight and reduced plasma levels of total cholesterol. Additionally, the analysis of the microbiota using 16S rRNA revealed that HCS improved dysbiosis by modulating the composition and abundance of specific bacterial genera, including F. rodentium, L. gasseri, L. reuteri, and L. murinus. These findings highlight the potential of HCS as a candidate for the treatment of obesity-related metabolic diseases.

Construction of Chitinase Complexes Using Self-Assembly Systems for Efficient Hydrolysis of Chitin

Chitin biomass is the second most abundant natural polysaccharide after cellulose on the earth, yet its recalcitrance to degrade and utilize severely limits its application. However, many microorganisms, such as Serratia marcescen, can secrete a range of free chitinases to degrade chitin, though their activity is typically insufficient to meet industrial demands. In this study, we employed self-assembly systems, named SpyTag/SpyCatcher and SnoopTag/SnoopCatcher, to modularize the molecular design of CHB, ChiB, ChiC, and CBP21 derived from S. marcescens ATCC14756, and we successfully constructed a variety of chitinase complexes. The assembled complexes showed higher chitinolytic activity and stability, compared to free chitinase mixture. Moreover, the distinct arrangements and combinations of chitinases within these complexes led to varied activities, suggesting that the spatial proximity and substrate channeling effects contribute to the synergy of chitinase complexes. The findings lay a solid technical foundation for the application of chitinosome in the industrial production of N-acetylglucosamine and chitooligosaccharides.

A thermal cross-linking approach to developing a reinforced elastic chitosan cryogel for hemostatic management of heavy bleeding

Uncontrolled hemorrhage stands as the primary cause of potentially preventable deaths following traumatic injuries in both civilian and military populations. Addressing this critical medical need requires the development of a hemostatic material with rapid hemostatic performance and biosafety. This work describes the engineering of a chitosan-based cryogel construct using thermo-assisted cross-linking with α-ketoglutaric acid after freeze-drying. The resulting cryogel exhibited a highly interconnected macro-porous structure with low thermal conductivity, exceptional mechanical properties, and great fluid absorption capacity. Notably, assessments using rabbit whole blood in vitro, as well as rat liver volume defect and femoral artery injury models simulating severe bleeding, showed the remarkable hemostatic performance of the chitosan cryogel. Among the cryogel variants with different chitosan molecular weights, the 150 kDa one demonstrated superior hemostatic efficacy, reducing blood loss and hemostasis time by approximately 73 % and 63 % in the hepatic model, and by around 60 % and 68 %, in the femoral artery model. Additionally, comprehensive in vitro and in vivo evaluations underscored the good biocompatibility of the chitosan cryogel. Taken together, these results strongly indicate that the designed chitosan cryogel configuration holds significant potential as a safe and rapid hemostatic material for managing severe hemorrhage.

Ultrasound-assisted extraction and antioxidant activity of polysaccharides from Tenebrio molitor

Tenebrio molitor, which is rich in various nutrients, and its polysaccharides, as significant bioactive substances, exhibit strong antioxidant effects. This study utilized defatted T. molitor as raw material and employed an ultrasound-assisted extraction method. The factors considered include extraction temperature, time, ultrasound power, and liquid-to-feed ratio, with the yield of T. molitor polysaccharides as the response value. Based on single-factor experiments and response surface methodology, the optimal extraction parameters for T. molitor polysaccharides were determined. Following purification, protein removal, and dialysis to eliminate impurities, the structure of the extracted polysaccharides was preliminarily investigated using infrared spectroscopy. Their antioxidant activities were explored by measuring their DPPH·, OH·, and ABTS+· radical scavenging abilities and Fe3+ reducing power. The results indicated that the optimal conditions for ultrasound-assisted extraction were an extraction temperature of 75 °C, an extraction time of 150 min, an ultrasound power of 270 W, and a liquid-to-feed ratio of 15:1 mL/g, yielding a polysaccharide extraction rate of 9.513%. Infrared spectroscopy analysis revealed the presence of pyranose sugars with main functional groups including C-O, C=O, and O-H. Antioxidant activity tests showed that within a certain concentration range, the higher the polysaccharide concentration, the stronger its radical scavenging abilities. Compared with Vitamin C(Vc), the polysaccharides had stronger scavenging abilities for DPPH· and OH·, some scavenging ability for ABTS+·, and Fe3+ reduction ability, and corresponding to IC50 values of 0.9625, 9.1909, and 235.69 mg/mL respectively. The Fe3+ reducing power reached a maximum absorbance of 0.38899 at a concentration of 1.6 mg/mL. T. molitor polysaccharides demonstrate promising antioxidant activity and potential as functional ingredients in food, health products, and pharmaceuticals, providing new technical references for the development and utilization of T. molitor resources.

In vitro antifungal activity and in vivo edible coating efficacy of insect-derived chitosan against Botrytis cinerea in strawberry

Strawberry is a perishable fruit, susceptible to development of rot by a range of fungi, in particular Botrytis cinerea. Chitosan represents an alternative to agrochemicals for improving shelf-life and fighting fungal pathogens. A chitosan-based coating derived from pupal exuviae of Hermetia illucens has been recently formulated for improving shelf-life of strawberry stored at 4 °C and mixed condition (4 °C and room temperature). The effects of a decolored (PEDEC) and not decolored (PEND) chitosan from the black soldier fly were evaluated and compared with commercial chitosans from crustaceans (CCs), in vitro and in vivo. An inhibition/reduction of fungal growth and a disturbance of normal fungal morphology were observed, being MIC of 0.5 mg mL-1 and 1 mg mL-1 and growth inhibition of 70 % and 4% for PEND and PEDEC, respectively. Both edible coatings distributed via aerograph showed equal or better potential application than CCs in controlling B. cinerea in strawberry post-harvest treated. Different effects for chitosans depended on their different molecular weight and deacetylation degree distributions, and the presence or absence of melanin pigments in their structure. PEND could act directly against the fungus, with effects predominantly associated with fungitoxic properties; PEDEC might principally provide viable alternatives, such as the elicitation of biochemical defense responses in fruits, for example through total phenols, in particular the flavonoids.

J. A, Sethupathy A. M, S. S, Alrashdi YBA, Ibrahim AE, El Deeb S. Current Status and Global Research Trend Patterns of Insect Meal in Aquaculture From Scientometric Perspective: (2013-2022)

In the past decade, insect meal has gained popularity in the animal feed industry, particularly in aquafeed, due to rising costs and decreased availability of fish meal (FM) and fish oil. Initially met with skepticism, insect meal is now seen as a promising ingredient because of its high nutrient profile. Research worldwide is exploring its potential as a FM replacement. Insects are abundant, nutritious, and environmentally friendly, as they can be reared on organic waste, minimizing the need for land, water, and energy. This research aims at obtaining a comprehensive and in-depth understanding of the current status and research trend patterns in this research field. To achieve this goal, this study conducts a mini systematic review and scientometric analysis of the global research published from 2013 to 2022 on the usage of insect meal in aquaculture. In the scientometric analysis, a total of 354 papers published by 1800 authors in 124 different journals from the Web of Science (WoS) core collection were analyzed, evaluating the number of publications, most relevant authors, organizations, top cited countries, most globally cited publications, and trending research themes in this field. The result showed that the University of Turin was the leading organization in insect meal research, whereas aquaculture was the leading journal, and author Laura Gasco was the prominent researcher in this field in the studied time frame (2013-2022). Italy was the leading country in Europe, while China dominated Asia in terms of the number of publications. The annual growth rate in insect meal research was found to be positive (23.11%), with 36.95 average citations per document. This study helps practitioners and scholars understand the current state of insect meal in aquaculture and identifies research requirements that can benefit both academia and industry.

The quantitative molecular weight-antimicrobial activity relationship for chitosan polymers, oligomers, and derivatives

Chitosan and chitosan derivatives can kill pathogenic microorganisms including bacteria and fungi. The antimicrobial activity is dependent on the degree of acetylation, substituent structure, and molecular weight. Over the past four decades, numerous studies have endeavored to elucidate the relationship between molecular weight and the activity against microorganisms. However, investigators have reported divergent and, at times, conflicting conclusions. Here a bilinear equation is proposed, delineating the relationship between antimicrobial activity, defined as log (1/MIC), and the molecular weight of chitosan and chitosan derivatives. Three constants AMin, AMax, and CMW govern the shape of the curve determined by the equation. The constant AMin denotes the minimal activity expected as the molecular weight tends towards zero while AMax represents the maximal activity observed for molecular weights exceeding CMW, the critical molecular weight required for max activity. This equation was applied to analyze data from seven studies conducted between 1984 and 2019, which reported MIC (Minimum Inhibitory Concentration) values against bacteria and fungi for various molecular weights of chitosan and its derivatives. All the 29 datasets exhibited a good fit (R2 ≥ 0.5) and half excellent (R2 ≥ 0.95) fit to the equation. The CMW generally ranged from 4 to 10 KD for datasets with an excellent fit to the equation.

Development of an efficient hemostatic material based on cuttlefish ink nanoparticles loaded in cuttlebone biocomposite

Traumatic hemorrhage is one of the main causes of mortality in civilian and military accidents. This study aimed to evaluate the effectiveness of cuttlefish bone (cuttlebone, CB) and CB loaded with cuttlefish ink (CB-CFI) nanoparticles for hemorrhage control. CB and CB-CFI were prepared and characterized using different methods. The hemostasis behavior of constructed biocomposites was investigated in vitro and in vivo using a rat model. Results showed that CFI nanoparticles (NPs) are uniformly dispersed throughout the CB surface. CB-CFI10 (10 mg CFI in 1.0 g of CB) showed the best blood clotting performance in both in vitro and in vivo tests. In vitro findings revealed that the blood clotting time of CB, CFI, and CB-CFI10 was found to be 275.4 ± 12.4 s, 229.9 ± 19.9 s, and 144.0 ± 17.5 s, respectively. The bleeding time in rat liver injury treated with CB, CFI, and CB-CFI10 was 158.1 ± 9.2 s, 114.0 ± 5.7 s, and 46.8 ± 2.7 s, respectively. CB-CFI10 composite resulted in more reduction of aPTT (11.31 ± 1.51 s) in comparison with CB (17.34 ± 2.12 s) and CFI (16.79 ± 1.46 s) (p < 0.05). Furthermore, CB and CB-CFI10 exhibited excellent hemocompatibility. The CB and CB-CFI did not show any cytotoxicity on human foreskin fibroblast (HFF) cells. The CB-CFI has a negative surface charge and may activate coagulation factors through direct contact with their components, including CaCO3, chitin, and CFI-NPs with blood. Thus, the superior hemostatic potential, low cost, abundant, simple, and time-saving preparation process make CB-CFI a very favorable hemostatic material for traumatic bleeding control in clinical applications.

Isolation and Structure Analysis of Chitin Obtained from Different Developmental Stages of the Mulberry Silkworm (Bombyx mori)

Chitin, a ubiquitous biopolymer, holds paramount scientific and economic significance. Historically, it has been primarily isolated from marine crustaceans. However, the surge in demand for chitin and the burgeoning interest in biopolymers have necessitated the exploration of alternative sources. Among these methods, the mulberry silkworm (Bombyx mori) has emerged as a particularly intriguing prospect. To isolate chitin from Bombyx mori, a chemical extraction methodology was employed. This process involved a series of meticulously orchestrated steps, including Folch extraction, demineralization, deproteinization, and decolorization. The resultant chitin was subjected to comprehensive analysis utilizing techniques such as attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), 13C nuclear magnetic resonance (NMR) spectroscopy, and wide-angle X-ray scattering (WAXS). The obtained results allow us to conclude that the Bombyx mori represents an attractive alternative source of α-chitin.

Preparation of nanochitin using deep eutectic solvents

Chitin is an abundant and renewable non-wood biopolymer. Nanochitin is formed by the assembly of chitin molecules, which has the advantages of large tensile strength, high specific surface area, and biodegradability, so it has been widely used. However, the traditional methods of preparing nanochitin have many drawbacks. As the new generation of green solvents, deep eutectic solvents (DESs) have been successfully applied in the fields of chitin dissolution, extraction, and nanochitin preparation. In this review, the relevant knowledge of chitin, nanochitin, and DESs was first introduced. Then, the application status of DESs in the fields of chitin was summarized, with a focus on the preparation of nanochitin using DESs. In conclusion, this review provided a comprehensive analysis of the published literature and proposed insights and development trends in the field of preparation of nanochitin using DESs, aiming to provide guidance and assistance for future researchers.

Physicochemical characterization of chitin extracted by different treatment sequences from an edible insect

Chitin present in the shell of edible insects is a potential source of chitin, lipids, and proteins, and it exerts various biological activities. Thus far, only a few studies have focused on the use of chitin as a source of high-protein-diet oligosaccharides. The use of insect chitin for the production of high-protein-diet oligosaccharides can lessen the reliance on diet crops. Moreover, although chitin composition in Tenebrio molitor larva, pupa, and adult has been extensively investigated, chitin extraction from T. molitor larval whole body and exuvium has received poor attention. The present study compared the effectiveness of two techniques for extracting high-protein-diet chitin oligosaccharide from an edible insect (T. molitor). Two different extraction sequences of chitin from the larval stage (molitor stage larvae) and adult stage (molitor stage adult) of edible T. molitor were investigated. Two processing steps were employed: (a) deproteinization (DEP) and (b) demineralization (DEM) treatments. Differences in the order, conditions, and period of their application resulted in two different chitin extraction procedures. The viscosity, degree of polymerization, and crystallinity index of the chitin extracted using the two procedures were measured, and its chemical components (chitin, ash, protein, fat, and moisture contents) were determined. T. molitor adults and larvae treated sequentially with DEM-DEP demonstrated the greatest yield of approximately 14.62 % ± 0.15 and 6.096 % ± 0.10 %, respectively. By contrast, when treated sequentially with DEP-DEM, the recorded yields were 10.96 % ± 0.18 and 5.31 % ± 0.38, respectively. Differences in the degree of deacetylation between both methods were observed. Additionally, Fourier transform infrared spectroscopy and X-ray diffractometry of the extracted chitin along with a commercial sample revealed consistent chain conformation, mean hydrogen bonding, and crystallinity index. In this way, residues produced by farmed edible insects can be recovered and used as a novel source of chitin.

Outer fold is sole effective tissue among three mantle folds with regard to oyster shell colour

Molluscs constitute the second largest phylum of animals in the world, and shell colour is one of their most important phenotypic characteristics. In this study, we found among three folds on the mantle edge of oyster, only the outer fold had the same colour as the shell. Transcriptome and mantle cutting experiment indicated that the outer fold may be mainly reflected in chitin framework formation and biomineralisation. There were obvious differences in SEM structure and protein composition between the black and white shell periostraca. The black shell periostraca had more proteins related to melanin biosynthesis and chitin binding. Additionally, we identified an uncharacterized protein gene (named as CgCBP) ultra-highly expressed only in the black outer fold and confirmed its function of chitin-binding and CaCO₃ precipitation promoting. RNAi also indicated that CgCBP knockdown could change the structure of shell periostracum and reduce shell pigmentation. All these results suggest that the mantle outer fold plays multiple key roles in shell periostraca bioprocessing, and shell periostracum structure affected by chitin-binding protein is functionally correlated with shell pigmentation. The investigation of oyster shell periostracum structure and shell colour will provide a better understanding in pigmentation during biological mineralisation in molluscs.

The Preparation and Physiochemical Characterization of Tenebrio molitor Chitin Using Alcalase

Chitin is mostly produced from crustaceans, but it is difficult to supply raw materials due to marine pollution, and the commonly used chemical chitin extraction method is not environmentally friendly. Therefore, this study aims to establish a chitin extraction process using enzymes and to develop edible insect-derived chitin as an eco-friendly new material. The response surface methodology (RSM) was used to determine the optimal conditions for enzymatic hydrolysis. The optimal conditions for enzymatic hydrolysis by RSM were determined to be the substrate concentration (7.5%), enzyme concentration (80 μL/g), and reaction time (24 h). The solubility and DDA of the mealworm chitosan were 45% and 37%, respectively, and those of the commercial chitosan were 61% and 57%, respectively. In regard to the thermodynamic properties, the exothermic peak of mealworm chitin was similar to that of commercial chitin. In the FT-IR spectrum, a band was observed in mealworm chitin corresponding to the C=O of the NHCOCH3 group at 1645 cm-1, but this band showed low-intensity C=O in the mealworm chitosan due to deacetylation. Collectively, mealworm chitosan shows almost similar physical and chemical properties to commercial chitosan. Therefore, it is shown that an eco-friendly process can be introduced into chitosan production by using enzyme-extracted mealworms for chitin/chitosan production.

Characterization of Spontaneous Melanization by Fluorescence Spectroscopy: A Basis for Analytical Application to Biological Substrates

Melanin is present in various biological substrates where it may participate in several processes, from innate immunity to the still-unsolved opposite roles in antioxidant protection, including photoprotection and the related ability to interact with light. Melanin–light interaction has also been an important source of inspiration for the development of innovative bioengineering applications. These are based on melanin’s light-energy-absorption ability of its chemically and structurally complex components and precursors, and on the improvement in analytical and diagnostic procedures in biomedicine. In this regard, here, we characterized the fluorescence spectral properties of melanin and of its precursor L-tyrosine in an aqueous solution during spontaneous melanization. Besides the confirmation of the typical fluorescence-emission signature of melanin and L-tyrosine, we provide additional insights on both emission and excitation spectra recorded during melanization. On these bases, we performed a subsequent characterization on the aqueous extracts from two different melanin-containing biological substrates, namely hairs from a domestic black cat and eggs from the Asian tiger mosquito. The results from the mild extraction procedure, purposely applied to obtain only the soluble components, combined with fluorescence spectral analysis are expected to promote further investigation of the melanization processes, particularly in insects.

Effect of dietary inclusion of mealworm frass on growth, hematology, and serum biochemistry of sheep

Frass is the main component of worm by-product which exhibit anti-microbial and anti-pathogenic properties. In the present study, we assessed the possibility of mealworm frass in sheep feeding regime and evaluated its effect on health and growth performance of sheep. A total of 09 experimental sheep (18-24 months of age) were grouped into three categories (T1, T3, and T3); each group comprised 3 animals including 2 males and 1 female. Group T1 was considered control, group T2 contains 75% commercial feed and 25 mealworm frass, and T3 was 50:50 of commercial feed and mealworm frass. The sheep in group T2 showed average weight gain of 2.9 kg; however, when the dietary inclusion increased up to 50% of mealworm frass or decreased up to 50% of concentrate feed, the average weight gain decreased up to 2.01 kg (group T3). Moreover, the sheep fed with 25% mealworm frass exhibited the lowest feed refusal percentage (6.33%) in total duration of the dietary period (6 weeks). The highest volume of RBC was found in blood collected from sheep fed within group T2 (10.22 10¹²/L ± 0.34), followed by sheep fed in group T3 (8.96 × 10¹²/L ± 0.99) (P < 0.05). Significantly (P < 0.05) highest MCV volume in fL (femtoliter) was found in group T2 (32.83 ± 0.44) followed by group T3 (31.23 ± 0.23). The animals in group T3 showed significantly (P < 0.05) highest MCHC volume (40.47 g/dL ± 0.62) followed by group T2 (38.77 ± 0.97). Similar trend was found in MPV (fL); significantly (P < 0.05) highest MPV volume was found in group T3 (12.63 ± 0.09) followed by group T2 (12.53 ± 0.33). Significantly (P < 0.05) high serum phosphorous (P) (6.00 ± 0.29), TG (60.03 ± 3.11), and TP (7.63 g/dL ± 0.23) levels were found in group T3, followed by animals in group T2. We can conclude that inclusion of mealworm frass to replace 25% commercial concentrate feed improved the growth rate and overall health status of the sheep. The present study laid a foundation for the utilization of the mealworm frass (waste product) in ruminant feeding.

A novel chitinous nanoparticles prepared and characterized with black soldier fly (Hermetia illucens L.) using steam flash explosion treatment

This is the first report of the use of steam flash explosion (SFE) to prepare chitinous nanoparticles from black soldier fly (BSF). SFE treatment was performed at a steam pressure of 0.45 to 1.60 MPa with a holding time of 60 s. As the pressure increased, the particle size of the chitinous particles decreased. Under SFE at 1.60 MPa, chitinous nanoparticles with sizes ranging from 59 to 162 nm were produced. SEM, AFM, Raman spectroscopy, FT-IR spectroscopy, ¹H NMR, TGA, and DSC were used to characterize the BSF chitin materials. It was demonstrated that SFE treatment deacetylated chitin to obtain chitosan with 91.24 % deacetylation. In addition, the polymer backbone was maintained, and the degree of polymerization of chitosan nanoparticles was reduced. The activity of the cationic groups of chitosan nanoparticles was improved, thereby enhancing the temperature sensitivity of the polymeric material. It can be concluded that the SFE one-step processing method is a simple and efficient way to prepare homogeneous biomaterial nanoparticles. This study has implications for the development of chitosan nanomaterials for biomedical applications.

Improved Antioxidant and Mechanical Properties of Food Packaging Films Based on Chitosan/Deep Eutectic Solvent, Containing Açaí-Filled Microcapsules

The development of biobased antioxidant active packaging has been valued by the food industry for complying with environmental and food waste concerns. In this work, physicochemical properties for chitosan composite films as a potential active food packaging were investigated. Chitosan films were prepared by solution casting, plasticized with a 1:2 choline chloride: glycerol mixture as a deep eutectic solvent (DES) and incorporated with 0-10% of optimized açaí oil polyelectrolyte complexes (PECs). Scanning electron microscopy and confocal laser scanning microscopy revealed that the chitosan composite films were continuous and contained well-dispersed PECs. The increased PECs content had significant influence on the thickness, water vapor permeability, crystallinity (CrD) and mechanical and dynamic behavior of the films, as well as their antioxidant properties. The tensile strength was reduced in the following order: 11.0 MPa (control film) > 0.74 MPa (5% DES) > 0.63 MPa (5% DES and 5% PECs). Films containing 2% of PECs had an increased CrD, ~6%, and the highest elongation at break, ~104%. Films with 1% of PECs displayed the highest antioxidant properties against the ABTS and DPPH radicals, ~6 and ~17 mg TE g^-1, respectively, and highest equivalent polyphenols content (>0.5 mg GAE g^-1). Films with 2% of particles were not significantly different. These results suggested that the chitosan films that incorporated 1-2% of microparticles had the best combined mechanical and antioxidant properties as a potential material for food packaging.

A flexible, high-efficiency, and low-cost FeS2@CTS hydrogel film for solar interface water evaporation

Solar interfacial water evaporation to obtain pure water has attracted extensive attention in recent years. In this work, based on the excellent optical property of FeS2 and the cross-linking nanostructure of chitosan (CTS), a FeS2@CTS hydrogel composite film for solar interfacial water evaporation was developed by hydrothermal synthesis and the following composite coating technology. The prepared FeS2@CTS presented high solar absorptivity of 95.27% and fast optical response capability. Under the optimized condition, the evaporation rate of pure water reached 3.34 kg m−2 h−1 and the photothermal conversion efficiency was 103.06% under one sun irradiation. In five runs, the evaporation rate of the FeS2@CTS was stable, indicating the excellent cycle stability. Also, in the desalination test, the stable evaporation rate of 1.74 kg m−2 h−1 was obtained in five runs. Due to the simple preparation method, low cost, and outstanding interfacial evaporation property, this FeS2@CTS indicates great potential for the seawater desalination or other photothermal conversion applications.

The Variety of Applications of Hermetia illucens in Industrial and Agricultural Areas-Review

Hermetia illucens (Diptera: Stratiomyidae, Linnaeus, 1978), commonly known as the black soldier fly (BSF), is a saprophytic insect, which in recent years has attracted significant attention from both the scientific community and industry. The unrestrained appetite of the larvae, the ability to forage on various organic waste, and the rapid growth and low environmental impact of its breeding has made it one of the insect species bred on an industrial scale, in the hope of producing fodder or other ingredients for various animals. The variety of research related to this insect has shown that feed production is not the only benefit of its use. H. illucens has many features and properties that could be of interest from the point of view of many other industries. Biomass utilization, chitin and chitosan source, biogas, and biodiesel production, entomoremediation, the antimicrobial properties of its peptides, and the fertilizer potential of its wastes, are just some of its potential uses. This review brings together the work of four years of study into H. illucens. It summarizes the current state of knowledge and introduces the characteristics of this insect that may be helpful in managing its breeding, as well as its use in agro-industrial fields. Knowledge gaps and under-studied areas were also highlighted, which could help identify future research directions.

Morphological and structural characterization of chitin as a substrate for the screening, production, and molecular characterization of chitinase by Bacillus velezensis

The processing of shellfishery industrial wastes is gaining much interest in recent times due to the presence of valuable components. Chitin is one of the valuable components and is insoluble in most common solvents including water. In this study, a novel gram-positive bacterial strain capable of solubilizing chitin was screened from a prawn shell dumping yard. The chitinolytic activity of the isolated strain was observed through the zone of hydrolysis plate assay. The hyper-producing isolate was identified as Bacillus velezensis through the 16S rRNA sequencing technique. The structural and morphological characterization of raw and colloidal chitin preparation was carried out using FTIR, XRD, and SEM analysis. The residual protein and mineral content, degree of polymerization, and degree of acetylation were reported for both raw and colloidal chitin preparations. There was a linear increase in the chitinase activity with an increase in the colloidal chitin concentration. The maximum activity of chitinase was observed as 38.98 U/mL for the initial colloidal chitin concentration of 1.5%. Supplement of additional carbon sources, viz., glucose and maltose, did not improve the production of chitinase and resulted in a diauxic growth pattern. The maximum chitinase activity was observed to be 33.10 and 30.28 U/mL in the colloidal chitin-containing medium with and without glucose as a secondary carbon source, respectively. Interestingly, the addition of complex nitrogen sources has increased the production of chitinase. A 1.95- and 2.14-fold increase in the enzyme activity was observed with peptone and yeast extract, respectively. The chitinase was confirmed using SDS-PAGE, native PAGE, and zymograms. The optimum pH and temperature for chitinase enzyme activity were found to be 7.0 and 44 °C, respectively.

Integrative analysis uncovers response mechanism of Pirata subpiraticus to chronic cadmium stress

Soil cadmium (Cd) pollution is global environmental pollution and adversely affects paddy field organisms. Wolf spider grants a new insight to evaluate the toxicity triggered by Cd, yet the impact of chronic Cd exposure on the spider and its molecular mechanism remains unclear. The present study found that the wolf spider Pirata subpiraticus fed with Cd-accumulated flies for 5 weeks presented lower catalase, peroxidase, and acetylcholinesterase activities and higher malonaldehyde content than the control spiders (p < 0.05). An in-depth transcriptomic analysis yielded a total of 5995 differentially expressed genes (DEGs, with 3857 up-regulated and 2138 down-regulated genes) from the comparison, and 19 DEGs encoding three enzymatic indicators were down-regulated. Further enrichment analysis indicated that Cd stress could inhibit the expression of cuticle and chitin-encoding genes via the down-regulation of several key enzymes, such as chitin synthase, glutamine-fructose-6-phosphate transaminase, and chitinase. In addition, our findings suggested that hedgehog and FoxO signaling pathways might play an essential role in regulating survival, cell cycle, and autophagy process in spiders, which were primarily down-regulated under Cd stress. An intensely interactive network displayed that Cd exposure could repress key biological processes in P. subpiraticus, particularly peptide metabolic process and peptide biosynthetic process. To sum up, this integrative investigation confirmed an effective bioindicator for assessing Cd-induced toxicity; provided a mass of genes, proteins, and enzymes for further validation; and granted novel perspectives to uncover the molecular responses of spiders to Cd pollution.

The Evaluation of the Biological Effects of Melanin by Using Silkworm as a Model Animal

Melanin has been reported to have potential applications in industries such as cosmetics and food due to its anti-UV and antioxidative qualities. However, the corresponding data on its safety evaluation or biological consequences are fairly limited; such data are critical given its widespread use. The effect of different concentrations (1, 2, 3, and 4%) of melanin on growth status (larvae length and weight, cocoon weight, and morphology), the microstructure of the various tissues (fat body, silk gland, and midgut), and silk properties was studied by using the silkworm (bombyx mori) as the model organism. The weight and length of silkworm larvae fed with melanin were lower than the control, indicating that melanin appears to have a negative effect on the growth status of silkworms; however, the histophysiology analysis indicates that the cell morphologies are not changed, the XRD and FTIR spectra indicate that the secondary and crystalline structures of silks are also well preserved, and the thermogravimetric analysis and tensile test indicate that the thermal stability and mechanical properties are well maintained and even improved to some extent. Generally, it indicates that melanin has a certain inhibitory effect on the growth of silkworm larva but causes no harm to the cell microstructures or silk properties; this demonstrates that the safety of melanin as a food addictive should be considered seriously. The increase of thermal stability and mechanical properties shows that melanin may be a good chemical modifier in textile industries.

Fluorescent Microscopy-Based Detection of Chitin in Intact Drosophila melanogaster

Chitin is the major scaffolding component of the insect cuticle. Ultrastructural analyses revealed that chitin adopts a quasi-crystalline structure building sheets of parallel running microfibrils. These sheets called laminae are stacked either helicoidally or with a preferred orientation of the microfibrils. Precise control of chitin synthesis is mandatory to ensure the correct chitin assembly and in turn proper function of cuticular structures. Thus, evaluation of chitin-metabolism deficient phenotypes is a key to our understanding of the function of the proteins and enzymes involved in cuticle architecture and more generally in cuticle biology in insects. Usually, these phenotypes have been assessed using electron microscopy, which is time-consuming and labor intensive. This stresses the need for rapid and straightforward histological methods to visualize chitin at the whole tissue level. Here, we propose a simple method of chitin staining using the common polysaccharide marker Fluorescent brightener 28 (FB28) in whole-mount Drosophila melanogaster. To overcome the physical barrier of FB28 penetration into the cuticle, staining is performed at 65°C without affecting intactness. We quantify FB28 fluorescence in three functionally different cuticular structures namely wings, dorsal abdomens and forelegs by fluorescence microscopy. We find that, as expected, cuticle pigmentation may interfere with FB28 staining. Down-regulation of critical genes involved in chitin metabolism, including those coding for chitin synthase or chitinases, show that FB28 fluorescence reflects chitin content in these organs. We think that this simple method could be easily applied to a large variety of intact insects.

Antiviral Polymers: A Review

Polymers, due to their high molecular weight, tunable architecture, functionality, and buffering effect for endosomal escape, possess unique properties as a carrier or prophylactic agent in preventing pandemic outbreak of new viruses. Polymers are used as a carrier to reduce the minimum required dose, bioavailability, and therapeutic effectiveness of antiviral agents. Polymers are also used as multifunctional nanomaterials to, directly or indirectly, inhibit viral infections. Multifunctional polymers can interact directly with envelope glycoproteins on the viral surface to block fusion and entry of the virus in the host cell. Polymers can indirectly mobilize the immune system by activating macrophages and natural killer cells against the invading virus. This review covers natural and synthetic polymers that possess antiviral activity, their mechanism of action, and the effect of material properties like chemical composition, molecular weight, functional groups, and charge density on antiviral activity. Natural polymers like carrageenan, chitosan, fucoidan, and phosphorothioate oligonucleotides, and synthetic polymers like dendrimers and sialylated polymers are reviewed. This review discusses the steps in the viral replication cycle from binding to cell surface receptors to viral-cell fusion, replication, assembly, and release of the virus from the host cell that antiviral polymers interfere with to block viral infections.

Antimicrobial and Antioxidant Activities of N-2-Hydroxypropyltrimethyl Ammonium Chitosan Derivatives Bearing Amino Acid Schiff Bases

N-2-hydroxypropyltrimethyl ammonium chloride chitosan (HACC), a cationic quaternary ammonium salt polymer exhibiting good solubility in water, is widely used because of its low toxicity and good biocompatibility. Herein, through ion exchange reaction, we prepared N-2-hydroxypropyltrimethyl ammonium chitosan derivatives bearing amino acid Schiff bases with good biological activities. The accuracy of the structures was verified by FT-IR and 1H NMR. The antibacterial activity, antifungal activity, and scavenging ability of DPPH radical and superoxide radical of HACC derivatives were significantly improved compared with that of HACC. In particular, HACGM (HACC-potassium 2-((2-hydroxy-3-methoxybenzylidene)amino)acetate) and HACGB (HACC-potassium 2-((5-bromo-2-hydroxybenzylidene)amino)acetate) showed good inhibitory effect on bacteria and fungi, including Staphylococcus aureus, Escherichia coli, Botrytis cinerea, and Fusarium oxysporum f. sp. cubense. The inhibition rate of HACGB on Staphylococcus aureus and Escherichia coli could reach 100% at the concentration of 0.1 mg/mL, and the inhibition rate of HACGM and HACGB on Botrytis cinerea and Fusarium oxysporum f. sp. cubense could also reach 100% at the concentration of 0.5 mg/mL. Improving antimicrobial and antioxidant activities of HACC could provide ideas and experiences for the development and utilization of chitosan derivatives.

Evaluation of Antibacterial and Antifungal Properties of Low Molecular Weight Chitosan Extracted from Hermetia illucens Relative to Crab Chitosan

This study shows the research on the depolymerisation of insect and crab chitosans using novel enzymes. Enzyme preparations containing recombinant chitinase Chi 418 from Trichoderma harzianum, chitinase Chi 403, and chitosanase Chi 402 from Myceliophthora thermophila, all belonging to the family GH18 of glycosyl hydrolases, were used to depolymerise a biopolymer, resulting in a range of chitosans with average molecular weights (Mw) of 6-21 kDa. The depolymerised chitosans obtained from crustaceans and insects were studied, and their antibacterial and antifungal properties were evaluated. The results proved the significance of the chitosan's origin, showing the potential of Hermetia illucens as a new source of low molecular weight chitosan with an improved biological activity.

Polysaccharides in Agro-Industrial Biomass Residues

The large-scale industrial use of polysaccharides to obtain energy is one of the most discussed subjects in science. However, modern concepts of biorefinery have promoted the diversification of the use of these polymers in several bioproducts incorporating concepts of sustainability and the circular economy. This work summarizes the major sources of agro-industrial residues, physico-chemical properties, and recent application trends of cellulose, chitin, hyaluronic acid, inulin, and pectin. These macromolecules were selected due to their industrial importance and valuable functional and biological applications that have aroused market interests, such as for the production of medicines, cosmetics, and sustainable packaging. Estimations of global industrial residue production based on major crop data from the United States Department of Agriculture were performed for cellulose content from maize, rice, and wheat, showing that these residues may contain up to 18%, 44%, and 35% of cellulose and 45%, 22%, and 22% of hemicellulose, respectively. The United States (~32%), China (~20%), and the European Union (~18%) are the main countries producing cellulose and hemicellulose-rich residues from maize, rice, and wheat crops, respectively. Pectin and inulin are commonly obtained from fruit (~30%) and vegetable (~28%) residues, while chitin and hyaluronic acid are primarily found in animal waste, e.g., seafood (~3%) and poultry (~4%).

Chitin and derivative chitosan-based structures - Preparation strategies aided by deep eutectic solvents: A review

The high molecular weight of chitin, as a biopolymer, challenges its extraction due to its insolubility in the solvents. Also, chitosan, as the N-deacetylated form of chitin, can be employed as a primary material for different industries. The low mechanical stability and poor plasticity of chitosan films, as a result of incompatible interaction between chitosan and the used solvent, have limited its industrialization. Deep eutectic solvents (DESs), as novel solvents, can solve the extraction difficulties of chitin, and the low mechanical stability and weak plasticity of chitosan films. Also, DESs can be considered for the different chitosan and chitin productions, including chitin nanocrystal and nanofiber, N,N,N-trimethyl-chitosan, chitosan-based imprinted structures, and DES-chitosan-based beads and monoliths. This review aims to focus on the preparation and characterization (chemistry and morphology) of DES-chitin-based and DES-chitosan-based structures to understand the influence of the incorporation of DESs into the chitin and chitosan structure.

Natural Polymers Used in Edible Food Packaging—History, Function and Application Trends as a Sustainable Alternative to Synthetic Plastic

In this review, a historical perspective, functional and application trends of natural polymers used to the development of edible food packaging were presented and discussed. Polysaccharides and proteins, i.e., alginate; carrageenan; chitosan; starch; pea protein, were considered. These natural polymers are important materials obtained from renewable plant, algae and animal sources, as well as from agroindustrial residues. Historically, some of them have been widely used by ancient populations for food packaging until these were replaced by petroleum-based plastic materials after World War II. Nowadays, biobased materials for food packaging have attracted attention. Their use was boosted especially because of the environmental pollution caused by inappropriate disposal of plastic packaging. Biobased materials are welcome to the design of food packaging because they possess many advantages, such as biodegradability, biocompatibility and low toxicity. Depending on the formulation, certain biopolymer-based packaging may present good barrier properties, antimicrobial and antioxidant activities Thus, polysaccharides and proteins can be combined to form diverse composite films with improved mechanical and biological behaviors, making them suitable for packaging of different food products.

Chitosan as a Valuable Biomolecule from Seafood Industry Waste in the Design of Green Food Packaging

Chitosan is a versatile biomolecule with a broad range of applications in food and pharmaceutical products. It can be obtained by the alkaline deacetylation of chitin. This biomolecule can be extracted using conventional or green methods from seafood industry residues, e.g., shrimp shells. Chitin has limited applications because of its low solubility in organic solvents. Chitosan is soluble in acidified solutions allowing its application in the food industry. Furthermore, biological properties, such as antioxidant, antimicrobial, as well as its biodegradability, biocompatibility and nontoxicity have contributed to its increasing application as active food packaging. Nevertheless, some physical and mechanical features have limited a broader range of applications of chitosan-based films. Green approaches may be used to address these limitations, leading to well-designed chitosan-based food packaging, by employing principles of a circular and sustainable economy. In this review, we summarize the properties of chitosan and present a novel green technology as an alternative to conventional chitin extraction and to design environmentally friendly food packaging based on chitosan.

Development of Chitosan Films from Edible Crickets and Their Performance as a Bio-Based Food Packaging Material

Edible insects have gained attention due to their impressive nutritional composition, as well as their efficient use of natural resources. However, a research gap remains on the applications of insect chitosan, especially as it relates to their potential use as food packaging material. Chitosan from two reared cricket species (Acheta domesticus and Gryllodes sigillatus) was evaluated for use as food packaging material. Cricket chitosan films (CCF) were structurally similar to commercial shrimp chitosan films (SCF) at controlled glycerol levels, as seen by shared spectral peaks in FT-IR analyses. Mechanical properties of CCF showed they had equal or greater tensile strength when compared to commercial SCF, although flexibility was lower. Scanning electron microscopy showed increased roughness of microstructure, likely increasing the tortuosity. As a result, CCF had improved water vapor permeability compared to commercial SCF. Melanin complexes present in cricket chitin and chitosan increased hydrophobicity and decreased light transmittance. This study also revealed that intrinsic species differences, which occur during insect and crustacean exoskeleton development, could have effects on the functionality of chitosan packaging materials. Overall, CCF were found to be as effective as commercial SCF, while providing additional advantages. CCF derived from reared crickets have good mechanical and barrier properties, and improved water resistance and light barrier characteristics. Edible cricket chitosan has the potential to be used as bio-based packaging material for food and pharmaceutical applications.

Recent progress in green and biopolymer based photocatalysts for the abatement of aquatic pollutants

Enormous research studies on the abatement of anthropogenic aquatic pollutants including organic dyes, pesticides, cosmetics, antibiotics and inorganic species by using varieties of semiconductor photocatalysts have been reported in recent decades. Besides, many of these photocatalysts suffer in real applications owing to their high production cost and low stability. In many cases, the photocatalysts themselves are being considered as secondary pollutants. To eliminate these drawbacks, the green synthesized photocatalysts and the use of biopolymers as photocatalyst supports are considered in recent years. In this context, recent developments in green synthesized metals, metal oxides, other metal compounds, and carbon based photocatalysts in water purification are critically reviewed. Furthermore, the pivotal role of biopolymers including chitin, chitosan, cellulose, natural gum, hydroxyapatite, alginate in photocatalytic removal of aquatic pollutants is comprehensively reviewed. The presence of functional groups, electron trapping ability, biocompatibility, natural occurrence, and low production cost are the major reasons for using biopolymers in photocatalysis. Finally, the summary and conclusion are presented along with existing challenges in this research area.

Iron Based Chitin Composite Films for Efficient Solar Seawater Desalination

Seawater desalination provides a convenient method for the sustainable production of fresh water. However, the preparation of low-cost, high-efficiency solar absorbers remains a huge challenge. To this end, our research group designed and produced a cheap absorber—a membrane made of natural polymer chitin with black FeS and Fe3O4, respectively. Due to the hierarchical pore structure, excellent photothermal performance and good hydrophilicity of the film, their water evaporation rates reached 1.47 kg/m2/h and 1.55 kg/m2/h under one sunlight, respectively. Under about 10 suns, the highest desalination efficiency of FeS/chitin and Fe3O4/chitin are 90% and 74%, respectively, and their salinities are also in line with the World Health Organization drinking water standards. These results indicate the potential of chitin-based nanomaterials as high-efficiency solar absorbers to produce fresh water.

A comprehensive survey upon diverse and prolific applications of chitosan-based catalytic systems in one-pot multi-component synthesis of heterocyclic rings

Heterocyclic compounds are among the most prestigious and valuable chemical molecules with diverse and magnificent applications in various sciences. Due to the remarkable and numerous properties of the heterocyclic frameworks, the development of efficient and convenient synthetic methods for the preparation of such outstanding compounds is of great importance. Undoubtedly, catalysis has a conspicuous role in modern chemical synthesis and green chemistry. Therefore, when designing a chemical reaction, choosing and or preparing powerful and environmentally benign simple catalysts or complicated catalytic systems for an acceleration of the chemical reaction is a pivotal part of work for synthetic chemists. Chitosan, as a biocompatible and biodegradable pseudo-natural polysaccharide is one of the excellent choices for the preparation of suitable catalytic systems due to its unique properties. In this review paper, every effort has been made to cover all research articles in the field of one-pot synthesis of heterocyclic frameworks in the presence of chitosan-based catalytic systems, which were published roughly by the first quarter of 2020. It is hoped that this review paper can be a little help to synthetic scientists, methodologists, and catalyst designers, both on the laboratory and industrial scales.

The Kinetics of Chitosan Degradation in Organic Acid Solutions

This paper presents a comparative study on chitosan degradation in organic acid solutions according to their different dissociation characteristics. More precisely, the aim of the study was to determine the kinetics of the degradation process depending on the different acid dissociation constants (pKa values). The scientists involved in chitosan to date have focused mainly on acetic acid solutions. Solutions of lactic, acetic, malic, and formic acids in concentrations of 3% wt. were used in this research. The progress of degradation was determined based on the intrinsic viscosity measurement, GPC/SEC chromatographic analysis, and their correlation. Changes in the viscosity parameters were performed at a temperature of 20 °C ± 1 °C and a timeframe of up to 168 h (7 days). The chemical structure and DDA of the initial chitosan were analyzed using 1H-NMR spectroscopy analysis. The results of this study can be considered of high importance for the purpose of electrospinning, production of micro- and nano-capsules for drug delivery, and other types of processing. Understanding the influence of the dissociation constant of the solvent on the kinetics of chitosan degradation will allow the selection of an appropriate medium, ensuring an effective and stable spinning process, in which the occurrence of polymer degradation is unfavorable.