Search Results (233)

The majority of studies of fungal utilization of chitosan are associated with the production of a specific enzyme, chitosanase, which catalyzes the hydrolytic cleavage of the macrochain. In our opinion, the development of approaches to obtaining materials with new functional properties based on non-destructive chitosan transformation by living organisms and their enzyme systems is promising. This study was conducted using a wide range of classical and modern methods of microbiology, biochemistry, and physical chemistry. The ability of the ascomycete Fusarium oxysporum Schltdl. to modify films of chitosan with average-viscosity molecular weights of 200, 450, and 530 kDa was discovered. F. oxysporum was shown to use chitosan as the sole source of carbon/energy and actively overgrew films without deformations and signs of integrity loss. Scanning electron microscopy (SEM) recorded an increase in the porosity of film substrates. An analysis of the FTIR spectra revealed the occurrence of oxidation processes and crosslinking of macrochains without breaking β-(1,4)-glycosidic bonds. After F. oxysporum growth, the resistance of the films to mechanical dispersion and the degree of ordering of the polymer structure increased, while their solubility in the acetate buffer with pH 4.4 and sorption capacity for Fe²⁺ and Cu²⁺ decreased. Elemental analysis revealed a decrease in the nitrogen content in chitosan, which may indicate its inclusion into the fungal metabolism. The film transformation was accompanied by the production of extracellular hydrolase (different from chitosanase) and peroxidase, as well as biosurfactants. The results obtained indicate a specific mechanism of aminopolysaccharide transformation by F. oxysporum. Although the biochemical mechanisms of action remain to be analyzed in detail, the results obtained create new ways of using fungi and show the potential for the use of Fusarium and/or its extracellular enzymes for the formation of chitosan-containing materials with the required range of functional properties and qualities for biotechnological applications. Full article

In this paper, mussel shells were used to produce chitin, chitosan, and calcium acetate using chemical processes, searching for an alternative environmentally friendly biopolymer and calcium source. Mussel shells were treated with acetic acid as a demineralizing agent, resulting in separate solid fractions and calcium solution. The solid was further purified to produce chitin by deproteinization and decolorization processes, and then the deacetylation process was used to obtain chitosan. The calcium solution was evaporated to produce calcium acetate powder. The yields of extracted chitin, chitosan, and calcium acetate from 100 g of mussel shells were 2.98, 2.70, and 165.23 g, respectively. The prepared chitin, chitosan, and calcium acetate were analyzed by Fourier transform infrared (FTIR) spectrophotometry, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and scanning electron microscope (SEM) to confirm the chemical and physical properties. The analysis results of chitin and chitosan revealed the similarity to chitosan derived from crustaceans and insects in terms of functional group, structure and morphologies. The prepared calcium acetate shows FTIR and XRD data corresponding to calcium acetate monohydrate (Ca(CH₃COO)₂·H₂O) similar to synthesized calcium acetate in previous research. In addition, the mineral contents of calcium acetate identified by X-ray fluorescence (XRF) analysis exhibit 97.8% CaO with non-toxic impurities. This work demonstrated the potential of the production process of chitin, chitosan, and calcium acetate for the development of a sustainable industrial process with competitive functional performance against the commercial chitin and chitosan production process using crustacean shells and supported the implementation of a circular economy. Full article

Apple pomace, a by-product from the production of concentrated juice, is a major contributor to global food waste. Despite its beneficial nutritional profile, apple pomace is predominantly disposed of in landfills. Rapid fermentation and spoilage caused by microorganisms are compounding factors in this demise, despite significant research into upcycling strategies. Thus, there is an unmet need for economical approaches that allow for the preservation of pomace during storage and transportation to centralized processing facilities from regional hubs. To address this challenge, we investigated the potential of different preservatives for preventing microbial growth and the spoilage of apple pomace, including antimicrobials (natamycin and iodine), polysaccharides (chitosan and fucoidan), and acetic acid. Spread plates for total microbial and fungal counts were employed to assess the effectiveness of the treatments. High concentrations (10,000 ppm) of chitosan were effective at reducing the microbial load and inhibiting growth, and in combination with antimicrobials, eliminated all microbes below detectable levels. Nevertheless, acetic acid at an equivalent concentration to commercial vinegar displayed the highest economic potential. Apple pomace submerged in 0.8 M acetic acid (3 kg pomace per liter) resulted in a five-log reduction in the microbial colony-forming units (CFUs) out to 14 days and prevented fermentation and ethanol production. These results provide a foundation for the short-term storage and preservation of apple pomace that could contribute to its upcycling. Full article

Chitosan films with potential application in triboelectric nanogenerators (TENGs) represent a promising approach to replace non-biobased materials in these innovative devices. In the present work, chitosan with varying molecular weights (MW) and degrees of deacetylation was dissolved in aqueous acetic acid (AA) at different acid concentrations. It was observed that the MW had a greater influence on the viscosity of the solution compared to either the acid concentration or deacetylation degree. Gel formation occurred in high-MW chitosan solutions prepared with low AA concentration. Films prepared from chitosan solutions, through solvent-casting, were used to prepare TENGs. The power output of the TENGs increased with higher concentrations of AA used in the chitosan dissolution process. Similarly, the residual AA content in the dried films also increased with higher initial AA concentrations. Additionally, hot-pressing of the films significantly improves the TENG power output due to the decrease in morphological defects of the films. It was demonstrated that a good selection of the acid concentration not only facilitates the dissolution of chitosan but also plays a key role in defining the properties of the resulting solutions and films, thereby directly impacting the performance of the TENGs. Full article

Chitosan and technical cashew nutshell liquid (CNSLt) have emerged as promising natural compounds due to their antimicrobial, immunomodulatory, and fermentation-modulating properties. This study aimed to evaluate the inclusion of chitosan and CNSLt as potential substitutes for the ionophore monensin on feed intake, ruminal fermentation, nitrogen balance, and microbial protein synthesis in steers. Five crossbred steers (Bos taurus), 18 months old with an average body weight of approximately 350 kg and fitted with permanent ruminal cannulas, were assigned to a 5 × 5 Latin square design. The experimental diets consisted of: (1) control (CON), (2) monensin (MON; 25 mg/kg of dry matter [DM]), (3) chitosan (CHI; ≥850 g/kg deacetylation degree, 375 mg/kg DM), (4) CNSLt (500 mg/kg DM), and (5) CNSLt + CHI (500 + 375 mg/kg DM). Supplementation with CHI or CNSLt + CHI reduced the intake of dry matter, crude protein, and neutral detergent fiber. Additionally, fecal excretion of whole corn kernels increased in these treatments. Ruminal fermentation parameters were affected, with the CNSLt + CHI treatment promoting higher molar proportions of propionate and acetate, along with reduced estimated methane emissions. However, purine derivatives, microbial protein synthesis, and nitrogen balance were not significantly affected by any of the treatments. These results suggest that CNSLt and CHI, particularly when combined, may serve as effective natural alternatives to monensin in high-grain diets for ruminants. Full article

Despite its broad application due to its affordability, biodegradability, and natural antimicrobial and antioxidant activities, chitosan (CS) still exhibits limitations in mechanical strength and barrier effectiveness. Owing to its unique chemical characteristics, itaconic acid (IT) presents potential as a compatibilizing agent in polymeric blend formulations. Biodegradable polymers composed of chitosan (CS), itaconic acid (IT), and starch (S) were synthesized using two polymerization methods. The first method involved grafting IT onto CS at varying ratios of IT (4%, 6%, and 8% wt.), using 1% v/v acetic acid/water as the solvent and potassium persulfate as the initiator. In the second approach, starch (S) was blended with the copolymer P(CS-g-IT) at concentrations of 1%, 3%, and 5%, utilizing water as the solvent and glacial acetic acid as a catalyst. The resulting biodegradable films underwent characterization through FTIR, TGA, SEM, and mechanical property analysis. To further explore the effects of combining IT, starch, and carbon black, the blends, referred to as P[(CS-g-IT)-b-S], were also loaded with carbon black. This allowed for the evaluation of the materials’ physicomechanical properties, such as viscosity, tensile strength, elongation, and contact angle. The findings demonstrated that the presence of IT, starch, and carbon black collectively improved the films’ mechanical performance, physical traits, and biodegradability. Among the samples, the blended copolymer with 1% starch exhibited the highest mechanical properties, followed by the grafted copolymer with 8% IT and the blended copolymer mixed with carbon black at 7%. In contrast, the blended copolymer with 5% starch showed the highest hydrophilicity and the shortest degradation time compared to the grafted copolymer with 8% IT and the blended copolymer mixed with 7% carbon black. Full article

Natural organic matter (NOM) in surface waters is a major challenge for drinking water treatment due to its role in the formation of disinfection byproducts (DBPs) during chlorination. This study evaluated the performance of chitosan, a biodegradable coagulant, dissolved in acetic, lactic, and L-ascorbic acids for NOM removal under three turbidity levels (403, 1220, and 5038 NTU). Jar tests were conducted using raw water from the Río Grande de Añasco (Puerto Rico), and TOC, DOC, and UV₂₅₄ were measured at multiple time points. TOC removal ranged from 39.8% to 74.3%, with the highest performance observed in high-turbidity water treated with chitosan–L-ascorbic acid. DOC and UV₂₅₄ reductions followed similar trends, with maximum removals of 76.4% and 76.2%, respectively. Estimated THM formation potential (THMFP) was reduced by up to 81.6%. Across all acids, flocculation efficiencies exceeded 95%. Compared to conventional aluminum-based coagulants, chitosan demonstrated comparable performance, while offering environmental benefits. These results confirm the potential of chitosan–acid systems for effective organic matter removal and DBP control, supporting their application as sustainable alternatives in drinking water treatment. Full article

Bio-nanocomposite films were prepared using chitosan, gelatin, and varying concentrations (0, 0.5, 1.0, 2.0, and 5.0 wt%) of titanium dioxide (TiO₂) nanoparticles in acetic acid via a casting method. The incorporation of TiO₂ nanoparticles into the bio-chitosan matrix enhanced ultraviolet (UV) absorption and improved the films’ physical, mechanical, and electrical properties. Additionally, the TiO₂-loaded films exhibited antimicrobial activity, contributing to the extended preservation of packaged products by inhibiting microbial growth. Notably, the bio-nanocomposite films containing 1.0 wt% TiO₂ exhibited an electroactive response, bending under relatively low electric field strength (250 V/mm), whereas the control film without TiO₂ required higher field strength (550 V/mm) to achieve bending. This indicates potential applications in electroactive actuators requiring precise movement control. Among the tested concentrations, films containing 0.5 wt% and 1.0 wt% TiO₂ (Formulas 7 and 8) demonstrated optimal performance. These films presented a visually appealing appearance with no tear marks, low bulk density (0.91 ± 0.04 and 0.85 ± 0.18 g/cm³), a satisfactory electromechanical response at 250 V/m (17.85 ± 2.58 and 61.48 ± 6.97), low shrinkage percentages (59.95 ± 3.59 and 54.17 ± 9.28), high dielectric constant (1.80 ± 0.07 and 8.10 ± 0.73), and superior UV absorption compared with pure bio-chitosan films, without and with gelatin (Formulas 1 and 6). Full article

With the increasing urgency of petroleum resource scarcity and environmental challenges, the development of degradable bio-based flame retardants has become crucial for enhancing the fire safety of organic materials. In this work, a phosphorus-containing chitosan derivative (CS-PPOA) was synthesized via a one-step protonation reaction between chitosan (CS) and phenylphosphinic acid (PPOA) under mild conditions. The resulting multifunctional flame-retardant coating was applied to polyester (PET) fabrics. Comprehensive characterization using FT-IR, XPS, and NMR confirmed the successful protonation of chitosan amino groups through electrostatic interactions, forming a stable ionic complex. The CS-PPOA solution exhibited excellent rheological properties and film-forming ability, producing films with over 80% optical transmittance and flexibility. Thermogravimetric analysis (TGA) revealed that CS-PPOA achieved char residue yields of 76.8% and 40.2% under nitrogen and air atmospheres, respectively, significantly surpassing those of acetic acid-protonated chitosan (CS-HAc). The limiting oxygen index (LOI) of CS-PPOA increased to 48.3%, and vertical burning tests demonstrated rapid self-extinguishing behavior. When applied to PET fabrics at a 15% loading, the LOI value improved from 20.3% (untreated fabric) to 27.8%, forming a dense char layer during combustion while completely suppressing melt dripping. Additionally, the coated fabric exhibited broad-spectrum antibacterial activity, achieving a 99.99% inhibition rate against Escherichia coli and Staphylococcus aureus. This study provides a novel strategy for the green and efficient preparation of multifunctional bio-based flame-retardant coatings. Full article

Drought and metal pollution severely impact plant growth. Root-associated extremophilic fungi can improve plant performance, and their encapsulation improves protection and effectiveness. This study optimized the encapsulation conditions for an extremophilic fungus with plant growth-promoting traits using alginate–chitosan capsules. An endophytic fungus was isolated from the roots of Neltuma chilensis from the Atacama Desert and identified via internal transcribed spacer (ITS) sequencing. Its plant growth-promoting traits, including exopolysaccharide, ammonium, siderophore, and indole acetic acid production and phosphorus solubilization, were evaluated. Freeze-dried Penicillium nalgiovense was encapsulated using jet-breaking extrusion, and capsule morphology and fungal survival were assessed via scanning electron microscope (SEM), confocal laser scanning microscopy (CLSM), and viability tests. Using Taguchi’s design, optimal conditions for sphericity (0.914 ± 0.002) and mean size (3.232 ± 0.087 mm) were achieved with 1% chitosan, a 5 cm distance to the gelation bath, and a 40 Hz vibration frequency. CLSM analysis confirmed the presence of the chitosan outer layer, revealing the capsule’s coating material encapsulating the fungus P. nalgiovense. The encapsulated fungus remained viable across disinfection times, demonstrating effective protection and gradual release. These findings emphasize the need for precise parameter control in fungal encapsulation, providing a basis for developing robust bioinoculants to support plant resilience in extreme environments. Full article

The Miradero Water Treatment Plant (MWTP) in Mayagüez, Puerto Rico, uses sodium hypochlorite (SH) as a disinfectant. However, SH reacts with humic substances present in surface water, forming disinfection by-products (DBPs) regulated by the U.S. EPA. This study evaluated whether chitosan, a biopolymer with known bactericidal properties, could reduce chlorine demand and improve disinfection. Chitosan, with a 75% degree of deacetylation and a molecular weight of 460 kDa, was solubilized in four acids (acetic, citric, hydrochloric, and L-ascorbic) and tested under two turbidity ranges (236.0 and 2556 NTU). Chlorine demand curves were generated, and coliform presence–absence (P–A) tests were performed to assess bactericidal effects. Results showed that chitosan-treated samples achieved disinfection at the breakpoint with lower SH doses. For water with a turbidity of 236.0 NTU, all chitosan-acid solutions reached the breakpoint at 3.60 mg/L of SH. At 2556 NTU, three solutions required 4.20 mg/L SH, while hydrochloric acid–chitosan required only 3.60 mg/L. All chitosan-treated samples tested negative for coliforms, while controls treated with SH alone tested positive. These findings demonstrate that chitosan enhances bacterial removal and reduces chlorine demand, potentially lowering DBP formation in water treatment. Full article

Vitexin and isovitexin are natural flavone C-glucosides that have numerous benefits for human health. However, their low oral bioavailability and poor gastrointestinal absorption dramatically restrict their potential medicinal uses. To overcome this challenge, chitosan-coated alginate microcapsules were prepared for intragastrical administration to rabbits. An LC-MS/MS method was developed and validated for the simultaneous determination of vitexin and isovitexin in the plasma of treated rabbits, using salicylic acid as the internal standard. Raw rabbit plasma samples were deproteinized using acetonitrile as a precipitation agent. Chromatographic separation was performed on a reversed-phase C18 column (100 mm × 4.6 mm, 3.5 µm), with an isocratic mobile solvent system comprising methanol and 0.1% acetic acid (40:60) as the mobile phase. All the analytes and the internal standard were ionized on a triple quadrupole mass spectrometer and electrospray ionization, operating in negative mode and multiple reaction monitoring. The analytical approach developed underwent validation in terms of system suitability, specificity, selectivity, LLOQ of 2 ng/mL, linearity (2.0–200 ng/mL, R² > 0.99), accuracy (the intra- and inter-day from 94 to 110% with the relative standard deviations no more than 8.7%, precision with the recoveries from 97% to 102%, matrix effect (90–100%), carry-over, dilution integrity (2 times), and stability at room and frozen temperature for up to 1 month, and all the parameters met FDA and EMA requirements for bioanalytical methods. The validated procedure was applied to measure the absorption of vitexin and isovitexin from encapsulated extracts in a pilot pharmacokinetic study on rabbit plasma. Compared to the raw traditional extracts, the microcapsules enhanced the bioavailability of vi-texin and isovitexin regarding C_max and AUC values. Full article

In this study, a full multilevel factorial design (2¹ × 3¹ × 2¹) × 2 was conducted to investigate the effects of molar mass of chitosan (CS), the type of acid used for dissolution, and the composition of the coagulation bath on the coagulation, mechanical properties, and swelling of the filaments. The results showed the statistical significance of the factors in the characteristics of these filaments. The coagulation followed Fick’s second law of diffusion, with an increase in the chitosan molar mass reducing the coagulation rate, as did the use of acetic acid instead of lactic acid. CS with higher molar mass produced filaments with larger diameters, but without a proportional increase in tensile strength. Swelling was influenced by the acid and composition of the coagulation bath. The interaction of CS with acid and the CS molar mass factor were the terms of greatest statistical significance. Crystallinity was higher for samples dissolved in aqueous solutions of acetic acid and coagulated with ethanol, while lactic acid induced greater structural disorder. Samples coagulated with ethanol presented more homogeneous surfaces, while methanol resulted in rougher filaments. These findings emphasize the critical role of processing conditions in tailoring the properties of CS filaments, providing valuable insights for their optimization for biomedical applications. Full article

Background: Systemic therapy is frequently utilized because of its easy accessibility, low cost, and high efficacy. However, it can be linked with systemic adverse effects and drug–drug interactions, especially in immunocompromised and poly-medicated patients. Topical antifungals, associated with a low risk of systemic adverse effects and drug–drug interactions, have emerged as the most suitable treatment option for patients with diabetic foot disease. However, the duration of topical treatment can extend up to 12 months. Consequently, there is a need to bolster these topical treatments with complementary therapies. Methods: The current study acquired approval from an ethics committee (code 24/241-E) and Clinical Trials (code NCT06485050). No patients were excluded, irrespective of comorbidities or the severity of onychomycosis. Patients included in the study were administered Ciclopirox 8% (consisting of ethyl acetate, 96% ethanol, ketostearyl alcohol, hydroxypropyl chitosan, and purified water) once daily for 6 months. This was supplemented with photodynamic therapy (three sessions in the first 2 months) using toluidine blue gel and a 635 nm diode laser lasting 10 min, as well as monthly debridement of the nail plate. Results: All patients (10/10) included in the study exhibited negative microbiological culture results 6 months after the study began. Of these, 90% (9/10) were clinically cured, and thus, fully cured. No adverse effects or complications secondary to the treatments were observed in any of the cases. The average Onychomycosis Severity Index (OSI) value was initially 18.50 ± 8.947, reduced to 10.30 ± 6.129 at 3 months, and finally fell to 4.10 ± 4.08 at the end of the treatment. Conclusions: The current study demonstrated the clinical improvement, mycological cure, effectiveness, and safety of combination therapy of ciclopirox 8% and photodynamic therapy over 6 months. Full article

The application of electrospinning technologies for the preparation of mats based on mucoadhesive polysaccharides, such as chitosan (CS), is an attractive strategy for the development of biopolymeric delivery systems for topical corticosteroids. In this work, an electrospinning technique is described for the preparation of CS-based mats doped with halloysite nanotubes (HNTs) with modified release of clobetasol propionate (CP). The optimized composition of the electrospinning solution was determined: 2.4% solution of CS in 46% acetic acid with addition of PEO (10% of CS mass) and HNTs (5% of CS mass); CP was introduced as an ethanol solution at the rate of 2 mg CP per 1 g of the obtained nonwoven material. The process parameters (the electrospinning voltage of 50–65 kV, the rotation speed of the spinning electrode of 10 min⁻¹, and the distance between the electrodes of 24 cm) were also optimized. The developed technology allowed us to obtain homogeneous nanofiber mats with excellent mechanical properties and biphasic drug release patterns (66% of CP released within 0.5 h and 88% of CP released within 6 h). The obtained nanofiber mats maintained the anti-inflammatory activity of corticosteroid at the level of free CP and showed no cytotoxicity. Full article