Search Results (46)

Chitin–glucan complex (CGC) is a naturally occurring heteropolysaccharide in which chitin chains are covalently integrated with β-glucans, forming a rigid structural framework in fungal and yeast cell walls. CGC exhibits a broad spectrum of functional properties, including antimicrobial, antioxidant, adsorption, and tissue-regenerative activities; however, its technological exploitation has been severely constrained by its intrinsic insolubility in water and most common solvents. In this work, CGC was isolated from Aspergillus niger mycelial biomass and, for the first time, completely dissolved in a precooled aqueous NaOH/urea solvent system (12 wt.% NaOH, 8 wt.% urea) within 5 min at ambient temperature, yielding a clear and stable solution. The influence of alkali concentration on dissolution efficiency and solution stability was systematically examined. Structural integrity and covalent linkage between chitin/chitosan and glucan segments were confirmed using FTIR spectroscopy, two-dimensional NMR, and electron microscopy. The degree of deacetylation determined by NMR was approximately 25%. Rheological analysis revealed concentration- and temperature-dependent sol–gel transitions, with well-defined storage and loss moduli during gelation. Crosslinking with epichlorohydrin enabled the fabrication of lightweight, highly porous three-dimensional CGC aerogels. In vitro cytocompatibility studies using NIH 3T3 fibroblasts demonstrated no detectable cytotoxicity over 72 h. These results establish a green, efficient route for CGC dissolution and processing and highlight the promise of CGC aerogels as sustainable biomaterials for biomedical and environmental applications. Full article

In this study, biopolymer chitosan–glucan from fruiting bodies of Agaricus bisporus (Cs-Agrif) was extracted and characterized as a sustainable alternative to commercial low molecular weight (LMW) chitosan obtained from crab shells (Cs-1). Cs-Agrif was prepared through an alkaline treatment process that included deproteination and deacetylation in the same step. The obtained sample was evaluated for its molecular weight, rheological behavior, degree of deacetylation (DD), crystallinity, and β-glucan and phenolic contents. Furthermore, the antioxidant properties of the prepared chitosan were determined under in vitro conditions using four spectrophotometric methods. Finally, its antimicrobial activity was tested against two pathogenic bacteria, one yeast, and mycotoxigenic fungi. Cs-Agrif had low molecular weight, of 45.70 ± 5.20 kDa, with pseudoplastic flow behavior. The degree of deacetylation was 92.7%. FT-IR and XRD analyses confirmed a chitosan-like structure and lower crystallinity in Cs-Agrif compared to pure commercial chitosan. The mushroom-derived chitosan contained β-glucans and phenols, indicating a chitosan–glucan complex. Antimicrobial assays showed low Cs-Agrif microbicidal concentrations (≤2.5 mg mL⁻¹) for Escherichia coli, Enterococcus faecalis, and Candida albicans. The growth of Aspergillus flavus was significantly reduced after five days of incubation. The laboratory-prepared Cs-Agrif exhibited strong antioxidant activity at 5 mg mL⁻¹, comparing to standards. Mushroom-derived chitosan–glucan biopolymer displays excellent physicochemical, antimicrobial, and antioxidant properties, confirming its potential use in biomedicine, food, and the pharmaceutical and cosmetic industries, among many others. Full article

Chitosan is recognized by its capacity to bind lipids based on the viscosity and degree of deacetylation. We analyzed the in vitro binding of Procambarus clarkii chitosan (PCC) with extra virgin olive oil and sunflower oil at temperatures and pH levels that approximate gastric-like conditions. In the tube test, 4 mg of PCC and 0.3 g of either EVO or of SO oils were mixed by stirring in test tubes with 4 mL of water acidified with HCl to a pH of 3. The PCC binding capability was determined by measuring the differences between the suspension without PCC and the suspension with PCC added. A scanning electron microscope (SEM) was utilized to further observe the uniformity and morphology of the emulsified PCC/oil hydrogels. In the test tube, PCC was shown to have a 1:11 (w/w) binding capacity for EVO and 1:15 (w/w) for SO. The SEM-based examination demonstrated a smooth surface with fine porosity of the microstructure of either PCC/oil hydrogel, proving successful emulsification. Under conditions similar to those in the stomach after a meal, including acidity, mixed composition, and temperature, PCC efficiently binds and emulsifies EVO and SO. Full article

Chitin and chitosan, versatile biopolymers extensively used in the food and cosmetic industries, are traditionally sourced from crustaceans. However, fungi such as Agaricus bisporus mushrooms present a sustainable, non-animal alternative. This study explored the potential of different Agaricus bisporus samples, including fresh mushrooms and production residues, as sources of chitin. Given that Agaricus bisporus mushrooms are also a rich source of ergosterol, the study additionally incorporated samples treated with supercritical carbon dioxide (scCO₂). The effects of deproteinisation conditions—specifically the number of successive extractions, sodium hydroxide concentration, and extraction time—were evaluated for fresh mushroom samples in terms of alkali-insoluble matter, chitin yields, and the degree of deacetylation (DD), with the latter determined by Fourier-transform infrared spectroscopy. The results indicated that extraction time had no statistically significant impact on AIM or chitin yield, while the DD increased with prolonged extraction, plateauing after 60 min. Higher sodium hydroxide concentrations enhanced deacetylation, but adversely affected extraction yields. No significant differences in chitin’s DD were observed between fresh mushroom and production residue samples, regardless of scCO₂ treatment. This study demonstrates the viability of recovering chitin from Agaricus bisporus mushroom bio-residues, including those treated with scCO₂, offering a sustainable and eco-friendly alternative for chitin production. Full article

Currently, acne therapy relies not only on specific drugs but also on complementary treatments, such as dermocosmetics. Several studies have reported the use of chitosan and alginate in scaffolds for drug delivery systems. These materials can be loaded with a product that exhibits anti-acne properties such as silk sericin, a protein with antioxidant, photoprotective, and moisturizing properties. Therefore, this study proposes the development of a chitosan/alginate scaffold, loaded with sericin, to serve as a dermocosmetic platform complementing the pharmacological treatment of acne. The moisture content of the alginate and chitosan was determined as 14.7 and 21%, respectively; the ash content, which is similar for both polymers, was approximately 5%. The employed chitosan had a deacetylation degree of 82%, as determined by infrared spectrometry and corroborated by potentiometry. This technique was also used to determine the mannuronic/guluronic ratio of the alginate [M/G = 1.3] and confirm the identity of each one of the polymers in the raw materials and the resulting scaffolds. The molecular weights of alginate, chitosan, and sericin were 85, 5.1, and 57.4 kDa, respectively. The pH [6.31] and total protein concentration of the sericin solution [c(SER) = 6.1 mg/mL] were determined using UV-visible spectrophotometry. Swelling and release studies indicated that, although there were varying degrees of cross-linking and certain variables to control, the mechanism that defines the nature of both processes (otherwise complementary) is the relaxation of the polymer chains. Full article

The properties of natural rubber foam (NRF) containing gamma-synthesized chitosan (CS) powder were investigated to address the growing demand for efficient methods to treat industrial wastewater contaminated with heavy metals. The CS powder was prepared by irradiating chitin (CT) powder with varying doses of gamma rays (0–100 kGy), followed by deacetylation using 40% sodium hydroxide (NaOH) at 100 °C for 1 h. The resulting CS powders were then mixed with natural rubber latex (NRL) at different contents (0, 3, 6, and 9 parts per hundred parts of rubber by weight; phr) and processed using Dunlop techniques to prepare the foam samples. The experimental findings indicated that the degree of deacetylation (%DD) of the CS powder increased initially with gamma doses up to 60 kGy but then decreased at 80 and 100 kGy. In addition, when the CS powder was incorporated into the NRF samples, there were increases in total surface area, density, compression set, and hardness (shore OO), with increasing gamma doses and CS contents. Furthermore, the determination of heavy metal adsorption properties for Cu, Pb, Zn, and Cd showed that the developed NRF sample exhibited high adsorption capacities. For instance, their removal efficiencies reached 94.9%, 82.5%, 91.4%, and 97.0%, respectively, in NRF containing 9 phr of 60 kGy CS. Notably, all adsorption measurements were determined using 3 cm × 3 cm × 2.5 cm specimens submerged in respective metal solutions, with an initial concentration of 25 mg/L. However, the removal capacity per unit mass of the sample (mg/g) showed less dependencies on CS contents, probably due to the higher density of CS/NRF composites in comparison to pristine NRF, resulting in a smaller volume of the former being submerged in the solution, subsequently suppressing the effects from CS in the adsorption. Lastly, tests on the reusability of the developed NRF indicated that the samples could be reused for up to three cycles, with the Cu removal capacity remaining relatively high (83%) in the sample containing 9 phr of 60 kGy CS. The overall outcomes implied that the developed NRF with the addition of gamma-synthesized CS not only offered effective and eco-friendly heavy metal adsorption capacity to improve public health safety and the environment from industrial wastewater but also promoted greener and safer procedures for the synthesis/modification of similar substances through radiation technologies. Full article

Chitosan is a biopolymer that can be subjected to a variety of chemical modifications to generate new materials. The properties of modified chitosan are affected by its degree of deacetylation (DDA), which corresponds to the percentage of D-glucosamine monomers in its polymeric structure. Potentiometric titration is amongst the simplest, most readily available, and most cost-effective methods of determining the DDA. However, this method often suffers from a lack of precision, especially for modified chitosan resins. This is in large part because the equation used to calculate the DDA does not consider the molecular weight of the chemically modified monomeric units. In this paper, we introduce a new equation that is especially suited for modified chitosan bearing three different types of monomers. To test this equation, we prepared naphthalene–chitosan resins and subjected them to potentiometric titration. Our results show that our new equation, which is truer to the real structure of the polymeric chains, gives higher DDA values than those of the routinely used equations. These results show that the traditional equations underestimate the DDA of modified chitosan resins. Full article

Acid mine drainage (AMD) is an environmental issue linked with mining activities, causing the release of toxic water from mining areas. Polyethersulphone (PES) membranes are explored for AMD treatment, but their limited hydrophilicity hinders their performance. Chitosan enhances hydrophilicity, addressing this issue. However, the effectiveness depends on chitosan’s degree of deacetylation (DD), determined during the deacetylation process for chitosan production. This study optimized the chitin deacetylation temperature, alkaline (NaOH) concentration, and reaction time, yielding the highest chitosan degree of deacetylation (DD) for PES/chitosan membrane applications. Prior research has shown that high DD chitosan enhances membrane antifouling and hydrophilicity, increasing contaminant rejection and permeate flux. Evaluation of the best deacetylation conditions in terms of temperature (80, 100, 120 °C), NaOH concentration (20, 40, 60 wt.%), and time (2, 4, 6 h) was performed. The highest chitosan DD obtained was 87.11% at 80 °C, 40 wt. %NaOH at 4 h of chitin deacetylation. The PES/0.75 chitosan membrane (87.11%DD) showed an increase in surface hydrophilicity (63.62° contact angle) as compared to the pristine PES membrane (72.83° contact angle). This was an indicated improvement in membrane performance. Thus, presumably leading to high contaminant rejection and permeate flux in the AMD treatment context, postulate to literature. Full article

Shrimp waste is a valuable source for chitin extraction and consequently for chitosan preparation. In the process of obtaining chitosan, a determining step is the chitin deacetylation. The main characteristic of chitosan is the degree of deacetylation, which must be as high as possible. The molar mass is another important parameter that defines its utilizations, and according to these, high or low molar masses are required. The present study is an attempt to optimize the deacetylation step to obtain chitosan with a high degree of deacetylation and high or low molar mass. The study was carried out based on experimental data obtained in the frame of a central composite design where three working parameters were considered: NaOH concentration, liquid:solid ratio, and process duration. The regression models defined for the degree of deacetylation (DD) and for the mean molar mass (MM) of chitosan powders were used in the formulation of optimization problems. The objectives considered were simultaneous maximum DD and maximum/minimum MM for the final chitosan samples. For these purposes, multiobjective optimization problems were formulated and solved using genetic algorithms implemented in Matlab^®. The multiple optimal solutions represented by trade-offs between the two objectives are presented for each case. Full article

Chitosan is a linear biopolymer composed of D-glucosamine and N-acetylglucosamine units. The percentage of D-glucosamine in the polymeric chain can vary from one sample to another and is expressed as the degree of deacetylation (DDA). Since this parameter has an impact on many properties, its determination is often critical, and potentiometric titration is a common analytical technique to measure the DDA. Cross-linking with glutaraldehyde is one of the most explored modifications of chitosan; however, the determination of the DDA for the resulting reticulated chitosan resins can be challenging. In this paper, we report a new, rapid, and efficient method to determine the DDA of glutaraldehyde-cross-linked chitosan resins via HPLC. This method relies on the use of 2,4-dinitrophenylhydrazine (DNPH) as a derivatizing agent to measure the level of reticulation of the polymer (LR) after the reticulation step. In this study, we prepare three calibration curves (with an R² value over 0.92) for three series of reticulated polymers covering a large range of reticulation levels to demonstrate that a correlation can be established between the LR established via HPLC and the DDA obtained via titration. The polymers are derived from three different chitosan starting materials. These standard calibration curves are now used on a routine basis in our lab, and the HPLC method has allowed us to change our DDA analysis time from 20 h to 5 min. Full article

Chitosanases play a significant part in the hydrolysis of chitosan to form chitooligosaccharides (COS) that possess diverse biological activities. This study aimed to enhance the productivity of Paenibacillus elgii TKU051 chitosanase by fermentation from chitinous fishery wastes. The ideal parameters for achieving maximum chitosanase activity were determined: a squid pens powder amount of 5.278% (w/v), an initial pH value of 8.93, an incubation temperature of 38 °C, and an incubation duration of 5.73 days. The resulting chitosanase activity of the culture medium was 2.023 U/mL. A chitosanase with a molecular weight of 25 kDa was isolated from the culture medium of P. elgii TKU051 and was biochemically characterized. Liquid chromatography with tandem mass spectrometry analysis revealed that P. elgii TKU051 chitosanase exhibited a maximum amino acid identity of 43% with a chitosanase of Bacillus circulans belonging to the glycoside hydrolase (GH) family 46. P. elgii TKU051 chitosanase demonstrated optimal activity at pH 5.5 while displaying remarkable stability within the pH range of 5.0 to 9.0. The enzyme displayed maximum efficiency at 60 °C and demonstrated considerable stability at temperatures ≤40 °C. The presence of Mn²⁺ positively affected the activity of the enzyme, while the presence of Cu²⁺ had a negative effect. Thin-layer chromatography analysis demonstrated that P. elgii TKU051 chitosanase exhibited an endo-type cleavage pattern and hydrolyzed chitosan with 98% degree of deacetylation to yield (GlcN)₂ and (GlcN)₃. The enzymatic properties of P. elgii TKU051 chitosanase render it a promising candidate for application in the production of COS. Full article

Chitosan, which is a derivative of chitin, is particularly popular due to its biodegradable and renewable nature. However, the properties of chitosan can be inconsistent due to the extraction process and its natural origin, which poses a challenge to its use in composite materials as a matrix. The properties of chitosan can be tuned by controlling the degree of deacetylation (the extent to which acetyl groups are removed from chitin to form chitosan) and molecular weight. This paper presents a detailed study on the extraction and characterization of chitosan from shrimp shells. The structural thermal and mechanical characterization were studied using several techniques: Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and differential scanning calorimetry. The intrinsic viscosity and deacetylation degree were determined using various methods. The results showed an average degree of deacetylation of 77%. The chitosan films exhibited a high tensile strength of 43.9 MPa and an elongation at break of 3.14%. The thermal analysis revealed that the films had a glass transition temperature of 88 °C and a maximum thermal degradation temperature of 320 °C. The findings of this research could contribute to the development of chitosan-based materials with improved properties, leading to its wider adoption in the future for composite matrix application. The simple and efficient method used for the extraction and purification of chitosan from shrimp shells makes it a cost-effective and eco-friendly alternative to synthetic polymers. Full article

The main goal of this investigation is to conduct a thorough analysis of the physical, chemical, and morphological characteristics of chitosan derived from various forest fungi. Additionally, the study aims to determine the effectiveness of this vegetal chitosan as an antimicrobial agent. In this study, Auricularia auricula-judae, Hericium erinaceus, Pleurotus ostreatus, Tremella fuciformis, and Lentinula edodes were examined. The fungi samples were subjected to a series of rigorous chemical extraction procedures, including demineralization, deproteinization, discoloration, and deacetylation. Subsequently, the chitosan samples were subjected to a comprehensive physicochemical characterization analysis, encompassing Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), X-ray diffraction (XRD), degree of deacetylation determination, ash content determination, moisture content determination, and solubility determination. To evaluate the antimicrobial efficacy of the vegetal chitosan samples, two different sampling parameters were employed, namely human hand and banana, to assess their effectiveness in inhibiting microbial growth. Notably, the percentage of chitin and chitosan varied significantly among the distinct fungal species examined. Moreover, EDX spectroscopy confirmed the extraction of chitosan from H. erinaceus, L. edodes, P. ostreatus, and T. fuciformis. The FTIR spectra of all samples revealed a similar absorbance pattern, albeit with varying peak intensities. Furthermore, the XRD patterns for each sample were nearly identical, with the exception of the A. auricula-judae sample, which exhibited sharp peaks at ~37° and ~51°, while the crystallinity index of this same sample was approximately 17% lower than the others. The moisture content results indicated that the L. edodes sample was the least stable, while the P. ostreatus sample was the most stable, in terms of degradation rate. Similarly, the solubility of the samples showed substantial variation among each species, with the H. erinaceus sample displaying the highest solubility among the rest. Lastly, the antimicrobial activity of the chitosan solutions exhibited different efficacies in inhibiting microbial growth of skin microflora and microbes found on the peel of Musa acuminata × balbisiana. Full article

Chitosan (CS), a biopolymer derived from chitin, is known for strong antifungal activity while being biodegradable, biocompatible, and non-toxic. Because of its characteristic it has been widely used in control of fungal pathogens. Antifungal activity of chitosan can be further enhanced by obtaining chitosan nanoparticles (CSNPs). However, most of the experiments using CS and CSNPs as antifungal agents were performed under various conditions and using diverse CS batches of different characteristics and obtained from different sources. Therefore, it is essential to systematize the available information. This work contains a current review on how the CS parameters: molecular weight, degree of deacetylation, acetylation pattern and dispersity of these features shape its antifungal activity. It also considers how concentration and protonation (pH) of CS water solutions define final biological effect. Review explains in detail how CS parameters affect characteristics of CSNPs, particle size, zeta potential, and dispersities of both and determine antifungal activity. In addition to the parameters of CS and CSNPs, the review also discusses the possible characteristics of fungal cells that determine their susceptibility to the substances. The response of fungi to CS and CSNPs varies according to different fungal species and their stages of development. The precise knowledge of how CS and CSNP parameters affect specific fungal pathogens will help design and optimize environmentally friendly plant protection strategies against fungi. Full article

The accessibility of DNA to different cellular functions requires a dynamic regulation of chromatin organization that is mediated by different epigenetic modifications, which regulate chromatin accessibility and degree of compaction. These epigenetic modifications, particularly the acetylation of histone H4 in lysine 14 (H4K16ac), determine the degree of chromatin accessibility to different nuclear functions, as well as to DNA damage drugs. H4K16ac is regulated by the balance between two alternative histone modifications, acetylation and deacetylation, which are mediated by acetylases and deacetylases. Tip60/KAT5 acetylates, and SIRT2 deacetylates histone H4K16. However, the balance between these two epigenetic enzymes is unknown. VRK1 regulates the level of H4K16 acetylation by activating Tip60. We have shown that the VRK1 and SIRT2 are able to form a stable protein complex. For this work, we used in vitro interaction, pull-down and in vitro kinase assays. In cells, their interaction and colocalization were detected by immunoprecipitation and immunofluorescence. The kinase activity of VRK1 is inhibited by a direct interaction of its N-terminal kinase domain with SIRT2 in vitro. This interaction causes a loss of H4K16ac similarly to the effect of a novel VRK1 inhibitor (VRK-IN-1) or VRK1 depletion. The use of specific SIRT2 inhibitors in lung adenocarcinoma cells induces H4K16ac, contrary to the novel VRK-IN-1 inhibitor, which prevents H4K16ac and a correct DNA damage response. Therefore, the inhibition of SIRT2 can cooperate with VRK1 in the accessibility of drugs to chromatin in response to DNA damage caused by doxorubicin. Full article