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Chitin, as the main component of the exoskeleton of Arthropoda, is a highly available natural polymer that can be processed into various value-added products. Its most important derivative, i.e., chitosan, comprising β-1,4-linked 2-amino-2-deoxy-β-d-glucose (deacetylated d-glucosamine) and N-acetyl-d-glucosamine units, can be prepared via alkaline deacetylation process. Chitosan has been used as a biodegradable, biocompatible, non-antigenic, and nontoxic polymer in some in-vitro applications, but the recently found potentials of chitosan for in-vivo applications based on its biological activities, especially antimicrobial, antioxidant, and anticancer activities, have upgraded the chitosan roles in biomaterials. Chitosan approval, generally recognized as a safe compound by the United States Food and Drug Administration, has attracted much attention toward its possible applications in diverse fields, especially biomedicine and agriculture. Despite some favorable characteristics, the chitosan's structure should be customized for advanced applications, especially due to its drawbacks, such as low drug-load capacity, low solubility, high viscosity, lack of elastic properties, and pH sensitivity. In this context, derivatization with relatively inexpensive and highly available mono- and di-saccharides to soluble branched chitosan has been considered a "game changer". This review critically scrutinizes the emerging technologies based on the synthesis and application of lactose- and galactose-modified chitosan as two important chitosan derivatives. Some characteristics of chitosan derivatives and biological activities have been detailed first to understand the value of these natural polymers. Second, the saccharide modification of chitosan has been discussed briefly. Finally, the applications of lactose- and galactose-modified chitosan have been scrutinized and compared to native chitosan to provide an insight into the current state-of-the research for stimulating new ideas with the potential of filling research gaps., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier Inc. All rights reserved.)

Depending on its physicochemical properties and antibacterial activities, chitosan can have a wide range of applications in food, pharmaceutical, medicine, cosmetics, agriculture, and aquaculture. In this experimental study, chitosan was extracted from shrimp waste through conventional extraction, microwave-assisted extraction, and conventional extraction under microwave process conditions. The effects of the heating source on the physicochemical properties and antibacterial activity were investigated. The results showed that the heating process parameters affected the physicochemical properties considerably. The conventional procedure yielded high molecular weight chitosan with a 12.7 % yield, while the microwave extraction procedure yielded a porous medium molecular weight chitosan at 11.8 %. The conventional extraction under microwave process conditions led to medium molecular weight chitosan with the lowest yield (10.8 %) and crystallinity index (79 %). Antibacterial assessment findings revealed that the chitosan extracted using the conventional method had the best antibacterial activity in the agar disk diffusion assay against Listeria monocytogenes (9.48 mm), Escherichia coli. (8.79 mm), and Salmonella Typhimurium (8.57 mm). While the chitosan obtained by microwave-assisted extraction possessed the highest activity against E. coli. (8.37 mm), and Staphylococcus aureus (8.05 mm), with comparable antibacterial activity against S. Typhimurium (7.34 mm) and L. monocytogenes (6.52 mm). Moreover, the minimal inhibitory concentration and minimal bactericidal concentration assays demonstrated that among the chitosan samples investigated, the conventionally-extracted chitosan, followed by the chitosan extracted by microwave, had the best antibacterial activity against the target bacteria., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Chitosan is one of the valuable products obtained from crustacean waste. The unique characteristics of chitosan (antimicrobial, antioxidant, anticancer, and anti-inflammatory) have increased its application in various sectors. Besides unique biological properties, chitosan or chitosan-based compounds can stabilize emulsions. Nevertheless, studies have shown that chitosan cannot be used as an efficient stabilizer because of its high hydrophilicity. Hence, this review aims to provide an overview of recent studies dealing with improving the emulsifying properties of chitosan. In general, two different approaches have been reported to improve the emulsifying properties of chitosan. The first approach tries to improve the stabilization property of chitosan by modifying its structure. The second one uses compounds such as polysaccharides, proteins, surfactants, essential oils, and polyphenols with more wettability and emulsifying properties than chitosan's particles in combination with chitosan to create complex particles. The tendency to use chitosan-based particles to stabilize Pickering emulsions has recently increased. For this reason, more studies have been conducted in recent years to improve the stabilizing properties of chitosan-based particles, especially using the electrostatic interaction method. In the electrostatic interaction method, numerous research has been conducted on using proteins and polysaccharides to increase the stabilizing property of chitosan., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023. Published by Elsevier B.V.)

Chitosan, an amino polysaccharide mostly derived from crustaceans, has been recently highlighted for its biological activities that depend on its molecular weight (MW), degree of deacetylation (DD), and acetylation pattern (AP). More importantly, for some advanced biomaterials, the homogeneity of the chitosan structure is an important factor in determining its biological activity. Here we review emerging enzymes and cell factories, respectively, for in vitro and in vivo preparation of chitosan oligosaccharides (COSs), focusing on advances in the analysis of the AP and structural modification of chitosan to tune its functions. By 'mapping' current knowledge on chitosan's in vitro and in vivo activity with its MW and AP, this work could pave the way for future studies in the field., Competing Interests: Declaration of interests No interests are declared., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Large amounts of agricultural waste, especially marine product waste, are produced annually. These wastes can be used to produce compounds with high-added value. Chitosan is one such valuable product that can be obtained from crustacean wastes. Various biological activities of chitosan and its derivatives, especially antimicrobial, antioxidant, and anticancer properties, have been confirmed by many studies. The unique characteristics of chitosan, especially chitosan nanocarriers, have led to the expansion of using chitosan in various sectors, especially in biomedical sciences and food industries. On the other hand, essential oils, known as volatile and aromatic compounds of plants, have attracted the attention of researchers in recent years. Like chitosan, essential oils have various biological activities, including antimicrobial, antioxidant, and anticancer. In recent years, one of the ways to improve the biological properties of chitosan is to use essential oils encapsulated in chitosan nanocarriers. Among the various biological activities of chitosan nanocarriers containing essential oils, most studies conducted in recent years have been in the field of antimicrobial activity. It was documented that the antimicrobial activity was increased by reducing the size of chitosan particles in the nanoscale. In addition, the antimicrobial activity was intensified when essential oils were in the structure of chitosan nanoparticles. Essential oils can increase the antimicrobial activity of chitosan nanoparticles with synergistic effects. Using essential oils in the structure of chitosan nanocarriers can also improve the other biological properties (antioxidant and anticancer activities) of chitosan and increase the application fields of chitosan. Of course, using essential oils in chitosan nanocarriers for commercial use requires more studies, including stability during storage and effectiveness in real environments. This review aims to overview recent studies on the biological effects of essential oils encapsulated in chitosan nanocarriers, with notes on their biological mechanisms., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2023 Elsevier B.V. All rights reserved.)

Chitosan (CS) was modified with two fatty acids, i.e., capric acid (CA) and palmitic acid (PA). Particle size (315.8 nm), zeta potential (31.8 mV), and viscosity (29.4 mPa.s) of CS-PA nanogels were lower than CS-CA nanogels (793.2 nm, 53.3 mV, and 70.7 mPa.s). First, hempseed oil-in-water Pickering nanoemulsions were stabilized by CS-based particles/maltodextrin (MD). Then, the emulsions were dried using an electrostatic collector-equipped spray dryer. The D 50 of re-dispersed emulsion powders with CS-PA/MD coating was 936 nm. According to the FE-SEM images, oil coated with CS-PA/MD showed higher porosity and C/O ratio at the particle surface compared to the CS-CA/MD coating leading to more oil leakage. In addition, the crystallinity of hempseed oil coated with CS-PA/MD was higher than the one coated with CS-CA/MD. These findings showed that submicron Pickering emulsion powders could be achieved by targeted modification of CS and using a spray dryer equipped with an electrostatic collector., (Copyright © 2022. Published by Elsevier Ltd.)

The effect of fatty acid type bonded to chitosan on the emulsifying properties of chitosan-based particles was investigated. Capric acid, myristic acid, and stearic acid were attached to chitosan chains. Longer fatty acids in the structure of chitosan lead to the better and more uniform formation of chitosan nanogels. The contact angle of chitosan, chitosan-capric acid, chitosan-myristic acid and chitosan-stearic acid were found to be 52.5°, 60.0°, 65.1° and 72.5°, respectively. Different chitosan nanogels were used to stabilize walnut oil emulsions, and the emulsion stabilized with chitosan-stearic acid nanogels had the lowest creaming index (15.2%). Stabilized emulsions with chitosans attached to longer chain acids were more adapted to the mechanism of Pickering emulsions, in addition to having higher viscosity as well as more gel-like behavior. In general, this study showed that emulsifying properties of chitosan could be improved by increasing the number of fatty acid carbons bonded to chitosan., (Copyright © 2022 Elsevier Ltd. All rights reserved.)

Organophosphorus (OP) compounds are one of the most hazardous chemicals used as insecticides/pesticide in agricultural practices. A large variety of OP compounds are hydrolyzed by organophosphorus hydrolases (OPH; EC 3.1.8.1). Therefore, OPHs are among the most suitable candidates that could be used in designing enzyme-based sensors for detecting OP compounds. In this work, a novel nanobiosensor for the detection of paraoxon was designed and fabricated. More specifically, OPH was covalently embedded onto chitosan and the enzyme-chitosan bioconjugate was then immobilized on negatively charged gold nanoparticles (AuNPs) electrostatically. The enzyme was immobilized on AuNPs without chitosan as well, to compare the two systems in terms of detection limit and enzyme stability under different pH and temperature conditions. Coumarin 1, a competitive inhibitor of the enzyme, was used as a fluorogenic probe. The emission of coumarin 1 was effectively quenched by the immobilized Au-NPs when bound to the developed nanobioconjugates. However, in the presence of paraoxon, coumarin 1 left the nanobioconjugate, leading to enhanced fluorescence intensity. Moreover, compared to the immobilized enzyme without chitosan, the chitosan-immobilized enzyme was found to possess decreased Km value by more than 50%, and increased Vmax and Kcat values by around 15% and 74%, respectively. Higher stability within a wider range of pH (2-12) and temperature (25-90°C) was also achieved. The method worked in the 0 to 1050 nM concentration ranges, and had a detection limit as low as 5 × 10(-11) M.

Organophosphorus (OP) compounds are extensively used in agricultural practice for pest management. However, their residues have a long half-life in the ecosystem as well as in the agro-products, posing a serious threat to human and animal health. Aryldialkylphosphatase (EC 3.1.8.1) is widely used in detoxification procedures. In the present study, aryldialkylphosphatase was immobilised on synthesised cross-linked nano-sized gel particles, also known as nanogels, in order to enhance the enzyme's physicochemical properties. Accordingly, a new nanogel consisting of chitosan and myristic acid (CMA nanogel) was synthesised and characterised by way of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The aryldialkylphosphatase-CMA nanogel conjugate was then assayed by FTIR, and its physicochemical characteristics were also investigated. The data obtained from SEM and TEM showed the nanogels to be homogenous spherical particles less than 50 nm in diameter. The proper formation of the nanogel and nanobioconjugate was also confirmed by FTIR spectra. In comparison with the free enzyme, the pH and thermal stability of the aryldialkylphosphatase were enhanced by the covalent immobilisation. Moreover, the immobilised enzyme could maintain approximately half of its activity over more than one month. The kinetic parameters of the aryldialkylphosphatase- CMA nanogel conjugate were also shown to undergo remarkable improvements, hence the synthesised CMA-nanogel could act as a promising support for aryldialkylphosphatase immobilisation. It is suggested that the aryldialkylphosphatase-CMA nanogel could be used for detoxifying paraoxon; a nerve agent. Further clinical experiments are underway. [ABSTRACT FROM AUTHOR]

This study was set to prepare a new active film by using a biodegradable bio-based source, i.e., corn starch. To achieve that, benzoic acid (BA) and chitosan (CS) were covalently bound and CS-BA nanogel was then obtained using self-assembly method. Subsequently, rosemary essential oil (REO) was encapsulated in CS-BA nanogel. Finally, REO in both free and encapsulated forms were incorporated in starch-carboxy methyl cellulose (CMC) films and their physical, mechanical and antimicrobial properties were studied. The films incorporating CS-BA nanogel had a higher water vapor permeability compared with the films containing REO. Moreover, film containing 0.2% CS-BA nanogel had the highest transparency and tensile strength. The REO and nanogel alone had inhibitory effects against Staphylococcus aureus ( S. aureus ) and by encapsulation, the inhibitory effect of REO was increased. By encapsulating REO in nanogel, both immediately (REO) and gradual (Nanogel) antimicrobial effect against S. aureus in the starch-CMC suspensions were obtained. [ABSTRACT FROM AUTHOR]

Fossil-derived products contribute significantly to greenhouse gas emissions. Transitioning from fossil-based to bio-based products is an effective solution to this problem. There has been substantial research on how biorefinery systems can help achieve such an aim. Marine shell-based biorefinery systems have been proposed in the past, but their environmental sustainability has not been empirically proven. So, the current study examines the environmental impacts of chitosan production as a promising biomaterial in a lobster shell-based biorefinery. The life cycle assessment approach is used to estimate the environmental impact and cumulative exergy demand of chitosan production. The present study also aims at environmentally scrutinizing two non-commercial scenarios, i.e., the replacement of sodium hydroxide with potassium hydroxide (labeled as Scenario 1) and chitosan production based on the biological extraction of chitin and the replacement of sodium hydroxide with potassium hydroxide (labeled as Scenario 2) against the conventional chitosan production (labeled as the Base Scenario). The findings show that 1 kg of conventional chitosan production in the developed biorefinery leads to 8.75E-05 DALY damage to human health and 2.60E+02 PDF.m2.yr damage to ecosystem quality, mainly due to chitin and sodium hydroxide. In comparison, chitosan production based on Scenario 1 and Scenario 2 can lead to a 17% and 23% reduction in damage to human health and 6% and 11% in damage to ecosystem quality, respectively. The developed biorefinery produces chitosan with a weighted environmental impact of 43 EUR2003, which can be discounted by 8% and 13% using Scenario 1 and Scenario 2, respectively. The findings indicate that chitosan production eliminates 2.32E+02 MJ/FU exergy from nature, that approximately 54% of it is related to the "non-renewable, fossil" category. Scenarios 1 and 2 correspond to approximately a saving of 13% and a growth of 71% in exergy removal from nature than the Base scenario, respectively. [Display omitted] • Lobster shell is used for chitosan production in a marine shell-based biorefinery. • The proposed biorefinery is environmentally surveyed by life cycle assessment. • Sodium hydroxide used in biorefinery contributes to 42% of human health damage. • 17% less damage to human health is caused by potassium hydroxide than sodium hydroxide. • Chitosan from the lobster shell eliminates 2.32E+02 MJ/FU exergy from nature. [ABSTRACT FROM AUTHOR]

Herbal essential oils such as Cuminum cyminum are natural antifungal agents consisting of many different volatile compounds. In the present study, encapsulation by chitosan (CS)–caffeic acid (CA) nanogel was used to improve antimicrobial activity and stability of the C. cyminum essential oils against Aspergillus flavus . An encapsulation efficiency of 85% based on the optical density spectra of the essential oil was achieved and as revealed through the release kinetics studies, 78% of the encapsulated oils were released during 1 week. The results obtained indicated that due to the volatility and instability of the oils when exposed to environmental factors, its encapsulation considerably improved its performance. More specifically, the minimum inhibitory concentration of free and encapsulated C. cyminum essential oils against A. flavus under sealed condition were at 650 and 350 ppm, respectively. Moreover, the encapsulated oils performed better (800 ppm), when tested under non-sealed condition while the free oils failed to caused fungal growth inhibition within the concentration range tested (up to 1000 ppm). This finding could be of great significance in medicinal plant remedies in order to achieve improved performance of herbal essential oils at lower concentrations and during longer time frames. [ABSTRACT FROM AUTHOR]

Highlights: [•] CS–Ci nanogel; a promising encapsulating material for M. piperita essential oils. [•] Enhanced antifungal activity of CS–Ci nanogel-encapsulated essential oils. [•] Nanogel-encapsulation led to higher antifungal activity under non-sealed condition. [ABSTRACT FROM AUTHOR]