Degree Of Deacetylation Research Articles

Advances in extraction, utilization, and development of chitin/chitosan and its derivatives from shrimp shell waste.

Shrimp consumption is in great demand among the seafood used globally. However, this expansion has resulted in the substantial generation and disposal of shrimp shell waste. Through literature search, it has been observed that since 2020, global scholars have shown unprecedented interest in shrimp shell waste and its chitin/chitosan. However, these new insights lack corresponding and comprehensive summarization and analysis. Therefore, this article provides a detailed review of the extraction methods, applications, and the latest research developments on chitin/chitosan from shrimp shells, including micro-nano derivatives, from 2020 to the present. The results indicate that chemical extraction remains the primary technique for the extraction and preparation of chitin/chitosan from shrimp shells. With further refinement and development, adjusting parameters in the chemical extraction process or employing auxiliary techniques such as microwave and radiation enable the customization of target products with different characteristics (e.g., deacetylation degree, molecular weight, and degree of acetylation) according to specific needs. Additionally, in pursuit of environmentally friendly, efficient, and gentle extraction processes, recent research has shifted toward microbial fermentation and green solvent methods for chitin/chitosan extraction. Beyond the traditional antibacterial, film-forming, and encapsulation functionalities, research into the applications of chitosan in biomedical, food processing, new materials, water treatment, and adsorption fields is gradually deepening. Chitin/chitosan derivatives and their modified products have also been a focal point of research in recent years. However, with the rapid expansion, the future development of chitin/chitosan and its derivatives still faces challenges related to the unclear mechanism of action and the complexities associated with industrial scale-up.

Improving the gel properties of Ficus pumila Linn. pectin by incorporating deacetylated konjac glucomannan

To improve the gelation behaviour of pectin, the effect of deacetylated konjac glucomannan (DKGM) with various deacetylation degrees (27.44 %, 44.32 %, 60.25 %, and 71.77 %) on the heat-induced gel characteristics of Ficus pumila Linn. pectin was studied. The hardness, chewiness, and adhesiveness of the gel increased as the degree of deacetylation increased from 27.44 % to 60.25 %, but decreased at 71.77 %. Additionally, DKGM addition resulted in higher apparent viscosity and non-Newtonian fluid behaviour in the composite gel. The incorporation of DKGM into the gel matrix strengthened the gel structure by promoting hydrogen bond formation and shortening relaxation time compared to the control. Scanning electron microscopy images revealed that the densification of the pectin gel network increased as the degree of deacetylation of konjac glucomannan rose from 27.44 % to 60.25 %, but then loosened when it exceeded 71.77 %. As the degree of deacetylation increased, the hydrophobic interaction between pectin and DKGM increased. Overall, the addition of DKGM effectively modulated the gel properties of Ficus pumila Linn. pectin, thus broadening its industrial application on different gel products.

Extraction, characterization and evaluation of antimicrobial activity of chitosan from adult Zophobas morio (Fabricius, 1776) (Coleoptera: Tenebrionidae)

The increasing demand for chitosan has led to the exploration of alternative sources, including insects. In this study, chitosan was extracted from Zophobas morio beetles with 19.17 % yield. FTIR and Raman Spectroscopy showed similar peaks in Z. morio chitosan (ZC) and commercial chitosan (CC). ZC showed low crystallinity (40.96 %) and high thermal residual mass (42.7 %) than CC. SEM imaging of ZC displayed pores ranging from 10 μm to 0.3 μm. EDX mapping revealed the homogenous presence of C, N and O elements. ZC exhibited low molecular weight (435.95 kDa) and low intrinsic viscosity (317.95 cm3/g) than CC (680.20 kDa and 480.87 cm3/g, respectively). Degree of deacetylation of ZC and CC was 96.24 % and 78.26 %, respectively. ZC showed antimicrobial activity against Escherichia coli (ATCC 25922), Klebsiella pneumoniae (ATCC 13883), Proteus mirabilis (ATCC 29906), Staphylococcus aureus (ATCC 25923), Enterococcus faecalis (ATCC 29212) and Candida albicans (ATCC 90028) with zones of inhibition ranging from 5 mm to 11 mm. The minimum bactericidal concentration of ZC against K. pneumoniae and P. mirabilis was lower than CC. This study suggests the applicability of insect chitosan as an antimicrobial agent in the food and pharmaceutical industries.

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.

Rheology, stability, and physicochemical properties of NaOH-tannic acid solvent for β-chitin dissolution

The applicability of chitin in food systems is limited by its poor solubility in ordinary solvents. This study explores a novel solvent system composed of sodium hydroxide and tannic acid (NaOH/TA) in combination with a repeated freeze-thaw process for dissolving chitin. The highest chitin solubility in 8% NaOH/0.3% TA and 10% NaOH/0.3% TA was 2.1% and 2.3% (w/v), respectively. The lower NaOH and excessive tannic acid content may lead to reduction of chitin solubility. We also observed a unique rheological property of the chitin/NaOH/TA system. A higher concentration of TA reduced the chitin solution's shear viscosity, storage modulus, loss modulus, and gelling temperature. Its shear viscosity decreases with increasing shear rate, showing a shear thinning behavior. When the chitin/NaOH/TA solution system was stored at 30oC, the crystalline degree of chitin decreased, and the diffraction peak shifted, suggesting the formation of different intermolecular forces. The TA contents show no significant effect on the crystallinity of chitin. With increased storage time, the molecular weight of chitin decreased, and the degree of deacetylation (DD) increased. These results underscore the potential applications of the chitin/NaOH/TA system in the food industry.

The production and biological activity of fungal chitosan from the mycelial waste of Rhizomucor miehei

In this study, waste biomass of industrial enzyme producer Rhizomucor miehei was used as an alternative source for fungal chitosan production. Fungal chitosan was obtained from mycelial waste at the deproteinization and deacetylation stages at different temperatures and times of alkali and acid treatment with different concentrations of sodium hydroxide (1–3 N) and acetic acid (2–4 %), respectively. High chitosan yield (70.6 mg/g) was reached at the optimized conditions when the concentration of NaOH (3 N), the deproteinization time (20 mins) and temperature ( 95℃), the concentration of acetic acid (4 %), the deacetylation time (6 hrs) and temperature (85℃). The fungal chitosan with a molecular weight of 14 kDa showed a deacetylation degree of 78 %. The XRD pattern showed two peaks at 2θ values of 9° and 19°. The antimicrobial activity of the fungal chitosan showed broad spectrum at low concentrations (125–250 µg/mL) against the test microorganisms. As wound healing activity, after five days post-scratching, the HaCaT cells cultured in the presence of fungal chitosan demonstrated a notable 57 % increase in migration rate. These findings underscored the efficacy of the produced fungal chitosan, highlighting its promising biological activities. This is the first report to evaluate the use of waste Rhizomucor miehei biomass as alternative source for chitosan.

Exploring the potential of chitosan from royal shrimp waste for elaboration of chitosan/bioglass biocomposite: Characterization and “in vitro” bioactivity

Exploiting royal shrimp waste to produce value-added biocomposites offers environmental and therapeutic benefits. This study proposes biocomposites based on chitosan and bioglass, using shrimp waste as the chitosan source. Chitin extraction and chitosan preparation were characterized using various analytical techniques. The waste composition revealed 24 % chitin, convertible to chitosan, with shells containing 77.33-ppm calcium. (X-ray diffraction) XRD analysis showed crystallinity index of 54.71 % for chitin and 49.14 % for chitosan. Thermal analysis indicated degradation rates of 326 °C and 322 °C, respectively. The degree of deacetylation of chitosan was 97.08 % determined by proton nuclear magnetic resonance (1H-NMR) analysis, with an intrinsic viscosity of 498 mL.g−1 and molar mass of 101,720 g/mol, showing improved solubility in 0.3 % acetic acid. Royal chitosan (CHR) was combined with bioglass (BG) via freeze-drying to create a CHR/BG biocomposite for bone surgery applications. The bioactivity of the CHR/BG was tested in simulated body fluid (SBF), revealing a biologically active apatite layer on its surface. Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) analysis confirmed enhanced bioactivity of the CHR/BG compared to commercial chitosan. The CHR/BG biocomposite demonstrated excellent apatite formation, validated by Scanning Electron Microscopy (SEM), highlighting its potential in bone surgery.

Enhancing freeze-thaw stability of frozen dough with deacetylated konjac glucomannan: The role of degree of deacetylation

The effect of different degrees of deacetylation (DDs) of deacetylated konjac glucomannan (DKGM) on the gluten structure, water state, and yeast activity of frozen dough was evaluated. The moderate DKGM group maintained a more continuous gluten network after three freeze-thaw cycles, as evidenced by an 8.67% increase in disulfide bond content and a 15.01% increase in α-helix content compared to the KGM group. DKGM effectively impeded bound water migration, with the moderate DKGM group retaining 8.28% more bound water than the KGM group after three freeze-thaw cycles. The stabilization of gluten structure and water state in frozen dough by DKGM resulted in higher yeast activity in the low and moderate deacetylation groups (DD = 31.31% and 50.24%). Additionally, DKGM enhanced the quality of frozen steamed bread. The results indicate that DKGM with a moderate DD (50.24%) effectively alleviates the quality deterioration of frozen dough. These findings suggest that DKGM has great potential as a novel cryoprotectant for frozen dough, with DD being a crucial factor in its cryoprotective effect.

Obtaining chitosan from chitine-containing uzbekistan raw materials and research of antimicrobial properties

The optimal conditions for the isolation of valuable natural biopolymers were revealed. chitosan from cysts of Artemia parthenogenetia in the Aral Sea and from pupae of the silkworm Bombyx mori. Chitosan (Chs) was obtained from cysts of A. parthenogenetia with a molecular weight of 89 kDa, degree of deacetylation (DDA)— 72% and solubility— 81.62%. It has been shown that it is possible to isolate Chs from silkworm pupae of sufficient purity with different molecular weights and DDA depending on the synthesis conditions and the degree of purification. Bombyx mori Chs has a higher molecular weight of 100–160 kDa, a high DDA— up to 90% and a solubility of 88%. IR spectroscopy, X-ray diffraction and elemental analysis have shown the purity of the isolated Chs from various sources. In chitin from A. parthenogenetia cysts of the Aral Sea, two types of modifications α and β with corresponding syngonies are observed, which confirms its polymorphic structure. The antibacterial activity of B. mori Chs has been shown, which tends to expand the spectrum of suppressed bacteria with increasing concentration and have a bactericidal effect on both gram-negative and gram-positive bacteria. Chs B. mori had an immunostimulating effect on living organisms, which allows us to recommend drugs based on Chs to strengthen the immune system.

Physicochemical Properties of Chitosan Extracted from Silkworm (Bombyx mori L.) Exuviae

This study investigated the chitosan content in various developmental stages of silkworms, specifically focusing on larval cuticle, moult exuviae and larval exuviae. The chitosan percentage varied significantly among different stages, with the highest content observed in bivoltine hybrid larval exuviae (19.37%) and the lowest in the 1st instar larval cuticle (9.93%). Chitosan content showed a consistent increase during moulting stages, reaching its peak in exuviae. The investigation extended to examine properties of chitosan, including moisture content, nitrogen content, ash content, degree of deacetylation (DD), solubility, viscosity and pH. Moisture content ranged from 5.80 to 7.84%, nitrogen content from 5.05 to 6.17%, ash content within 0.50 to 0.80% and DD from 85.10 to 92.71%. Solubility ranged from 92.25 to 98.25% and viscosity was measured between 47 and 58 cP. The pH values ranged from 6.72 to 7.49. These findings contribute valuable insights into the chitosan characteristics at different developmental stages of silkworms, providing a comprehensive understanding of its variations and potential applications.

Physicochemical Characterization of Oil and Chitosan Extracted from Cross Breed and Bivoltine Hybrid Silkworm Pupae: A Comparative Analysis

The oil and chitosan were extracted from silkworm pupae and analysed its physicochemical properties. Oil content in silkworm pupae ranged from 26 to 28 % on a dry weight basis. Notably, female pupae had a higher oil content (27.99 %) compared to males (27.03%). Further, bivoltine hybrids exhibited a slightly higher oil content (27.65 %) than cross breeds (27.30 %). In comparison to edible oils like groundnut oil and sunflower oil, the pupal oil showed favourable results in terms of moisture content, iodine value and saponification values, indicating quality similar to edible oils. However, acid value of silkworm pupal oil (1.570 mg KOH/g oil) was lower than that of groundnut oil (3.125 mg KOH/g oil). The acid value and peroxide value were found to be lower than three in pupal oil samples, revealed that pupal oil is good for edible purposes and indicates good oxidative stability. Among the samples, Chitosan content was higher 2.526% in the cross breed (PM × CSR2) than bivoltine hybrid 2.308%. Male silkworm pupae had a higher chitin content (3.242%) compared to female pupae (3.013%) and chitosan content was also higher (2.430%) in male pupae than in female pupae (2.345%). Pupal chitosan shows better solubility (99 %), degree of deacetylation (>85%) and ash content (<1%). These physicochemical properties were achieved the desired level for utilizing the silkworm pupal oil and chitosan as commercial utilization.

Mobile lab: A novel pathogen assay using the nucleic acid automatic assay system assisted by a self-contained microfluidic cassette and chitosan decorating magnetic particles

Microfluidic pathogen detection cartridges with integrated switching valves have gained significant attention. Traditionally, these microfluidic cartridges utilized magnetic beads for a “bind-wash-elute-reaction” protocol to extract DNA but often lacked PCR-based aerosol contamination validation and focused primarily on isothermal applications. There is room to improve these systems, such as using novel DNA extraction methods and integrating PCR as the gold standard. In this study, we developed chitosan-decorated magnetic (CDM) particles and incorporated them into a mass-produced, self-contained microfluidic cartridge for the first time. Our results demonstrated that the DNA can be efficiently enriched from the lysis buffer (pH 5) using 75 % degree of deacetylation and 1 % of chitosan-modified CDM particles (20 μL). The DNA extraction efficiency exceeded 90 %. The CDM particles enabled “in-situ PCR”, simplifying the on-chip detection process to a “bind-wash-reaction” protocol. Additionally, we developed a nucleic acid automatic assay system (NA3 system) featuring a fluid thermocycler, four-channel optical detection, magnet, microcontroller, and software. The entire assay, from sample preparation to detection, can be completed within approximately 60 minutes, simultaneously detecting 16 targets. The performance of the NA3 system was better than that of the pristine magnetic microparticles-based assay and the commercial magnetic beads kit-based assay. The linearity, specificity, multi-pathogen detection, and user-friendliness of the NA3 system were tested. We validated the NA3 system's performance in detecting food-borne and serum infectious pathogens, demonstrating its potential for use in resource-limited settings.

A crayfish chitosan-based bioactive film to treat vaginal infections: A sustainable approach

Polymicrobial communities are seen to be a sign of health, but they can turn detrimental when an excess of pathogenic species leads to recurring vaginal infections. This microbiological imbalance may decrease women's fertility, increasing also the risk of infection by Human Papillomavirus (HPV) and/or other sexually transmitted infections (STIs). There is a worldwide need for smart/sustainable solutions to tackle these types of infections. Hereupon, we investigated, as a potential solution, the use of crayfish chitosan-based membrane as a mucoadhesive, antimicrobial, biocompatible and biodegradable material. Chitosan was chemically extracted with a process yield of ca. 63 % and a degree of deacetylation of ca. 65 %. Further chitosan was characterized by FTIR, DSC, XRD and zeta potential. Antimicrobial and antioxidant activities were tested by microbicide concentration and ABTS methods. The extracted chitosan was confirmed to be antioxidant and antimicrobial against Escherichia coli, Candida albicans, Staphylococcus aureus (methicillin resistant and susceptible strains). Vaginal films using chitosan extracted from crayfish shells were produced by solvent casting, and the biological profile was tested in simulated vaginal fluid as a proof of concept. The main data showed that the vaginal films prepared were active against several microorganisms responsible for vaginal infections, demonstrating their potential in the field.

Effect of Synthesis Condition on Degree of Deacetylation of Chitosan from Shrimp Waste for Smart Film Applications

Shrimp is an Indonesian’s export commodity with high economic value increasing every year. Usually, shrimps are exported in the form of frozen shrimp without shells, heads, tails, and entrails. It resulted in the accumulation of shrimp waste leading to the increasing environmental pollution. Shrimp waste contains high contents of chitin which can be processed to a chitosan owing several benefits. The purpose of this study is to determine the optimum condition of the synthesis of chitosan from chitin isolated by the autolysis method. The deproteination was carried out by soaking the shrimp waste in an acidic solution (pH 2 – 3) for 10 d. The demineralization process was done by reacting the deproteinated solids in a hydrochloric acid solution at pH 0 – 1 for 24 h. Parameters varied in this study time (1 – 3 h), chitin to NaOH ratio (1:10 – 1:30 (w/v)), and temperature (60 – 120℃). The higher all parameters used, the higher the obtained degree of deacetylation (DD) which is in the range of 18.35±1.13 to 48.6±0.51%. On the other hand, the obtained yield decreased from 50.66±1.98% to 47.78±0.81%. The optimum condition was obtained at a synthesis temperature of 120℃, chitin to NaOH ratio of 1:20 g/mL, and time of 3 h producing chitosan with DD of 54.25 ± 2.27%, and yield of 47.7 ± 0.65%. Chitosan synthesized using optimum conditions produced a relatively homogeneous thin film. Polyaniline was then introduced to the film to obtain a smart film prototype. This smart film was able to detect the pH changes proven by the change in its color. The smart film also could be potentially used as a “smart pack” for detecting product decay which releases ammonia gas.

Impact of konjac glucomannan with varied deacetylation degrees on plant-based meat analogue: Study on the gel properties, digestibility, and microstructure

Polysaccharides are widely used to improve the quality of plant-based meat analogue (PMA). In this study, four kinds of konjac glucomannan (KG) with different deacetylation degrees (DD) were prepared, namely KG1 (native KG, DD = 0.00 %), KG2 (DD = 41.40 %), KG3 (DD = 80.01 %) and KG4 (DD = 89.07 %), and their effects on the quality of PMA were studied. Results manifested that KG3 improved the hardness (from 3017.16 g to 3307.16 g) and protein digestibility (from 49.65 % to 53.01 %) of PMA without reducing the P21, KG2 and KG4 were less effective than KG3, while KG1 led to a significant decline in the hardness and protein digestibility of PMA. The rheological properties and intermolecular force analysis showed that the partially deacetylated KG was more conducive to improving the G' of the protein system during heating and the proportion of covalent bonds in PMA. These findings suggested that partially deacetylated KG was more promising than native or highly deacetylated KG in PMA. Furthermore, scanning electron microscopy revealed that the morphology of KG gradually changed from fine filaments, to coarse filaments, short filaments and granules as DD increased. This study provides a theoretical basis for the application of partially deacetylated KG in PMA.

A new strain of Rhodococcus indonesiensis T22.7.1T and its functional potential for deacetylation of chitin and chitooligsaccharides.

Chitin, abundant in marine environments, presents significant challenges in terms of transformation and utilization. A strain, T22.7.1T, with notable chitin deacetylation capabilities, was isolated from the rhizosphere of Acanthus ebracteatus in the North Sea of China. Comparative 16S rDNA sequence analysis showed that the new isolate had the highest sequence similarity (99.79%) with Rhodococcus indonesiensis CSLK01-03T, followed by R. ruber DSM 43338T, R. electrodiphilus JC435T, and R. aetherivorans 10bc312T (98.97%, 98.81%, and 98.83%, respectively). Subsequent genome sequencing and phylogenetic analysis confirmed that strain T22.7.1T belongs to the R. indonesiensis species. However, additional taxonomic characterization identified strain T22.7.1T as a novel type strain of R. indonesiensis distinct from CSLK01-03T. This study refines the taxonomic description of R. indonesiensis and investigates its application in converting chitin into chitosan. The chitin deacetylase (RiCDA) activity of strain T22.7.1T was optimized, and the enzyme was isolated and purified from the fermentation products. Through optimization, the RiCDA activity of strain T22.7.1T reached 287.02 U/mL, which is 34.88 times greater than the original enzyme's activity (8.0 U/mL). The natural CDA enzyme was purified with a purification factor of 31.83, and the specific activity of the enzyme solution reached 1200.33 U/mg. RiCDA exhibited good pH and temperature adaptability and stability, along with a wide range of substrate adaptabilities, effectively deacetylating chitin, chitooligosaccharides, N-acetylglucosamine, and other substrates. Product analysis revealed that RiCDA treatment increased the deacetylation degree (DD) of natural chitin to 83%, surpassing that of commercial chitosan. Therefore, RiCDA demonstrates significant potential as an efficient deacetylation tool for natural chitin and chitooligosaccharides, highlighting its applicability in the biorefining of natural polysaccharides.

Design, synthesis and biological evaluation of novel SIRT3 inhibitors targeting both NAD+ and substrate binding sites for the treatment of acute myeloid leukemia

Acute myeloid leukemia (AML) represents a highly malignant subtype of leukemia with limited therapeutic options. In this study, we propose a novel therapeutic strategy for treating AML by inhibiting SIRT3 to regulate mitochondrial metabolism network involved in energy metabolism and epigenetic modifications essential for AML survival. A series of thieno [3,2-d]pyrimidine-6-carboxamide derivatives were designed and synthesized by structure-based strategy, 17f was documented to be a potent and acceptable selective SIRT3 inhibitor with IC50 value of 0.043 μM and exhibited profound anti-proliferative activity in MOLM13, MV4-11, and HL-60 cells. Through CETSA assay and the degree of deacetylation of intracellular SIRT3 substrates, we confirmed that 17f could effectively bind and inhibit SIRT3 activity in AML cells. Mechanistically, 17f suppressed mitochondrial function, triggered the accumulation of ROS, and significantly inhibited the production of ATP in AML cells. With the breakdown of mitochondrial function, 17f eventually induced apoptosis of AML cells. In addition, 17f also showed excellent anti-AML potential in nude mouse tumor models of HL-60-Luc. Collectively, these results demonstrate that 17f is a potent and acceptable selective SIRT3 inhibitor with promising potential to treat AML.

Effects of Gamma-Synthesized Chitosan on Morphological, Thermal, Mechanical, and Heavy-Metal Removal Properties in Natural Rubber Foam as Sustainable and Eco-Friendly Heavy Metal Sorbents

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.

INFLUENCES OF CROSSLINKER AND MOLECULAR WEIGHT OF CHITOSAN ON PHYSICO-CHEMICAL PROPERTIES OF ANTIBACTERIAL TREATED COTTON FABRICS

This study investigated the influences of crosslinking agent and molecular weight on the surface and comfort properties of cotton fabrics treated by chitosan. Two types of chitosan, with molecular weight (2.6 kDa and 187 kDa), with deacetylation degree (DD) of 75%, were used, along with two types of crosslinking agents: citric acid (CA) and dimethylol dihydroxyethyleneurea (DMDHEU). These agents were applied to cotton fabrics for antibacterial treatments. The treated cotton fabrics were evaluated using several quality indicators related to physico-chemical properties, including whiteness (according to ISO 105 J02), breathability (according to ASTM D737:2004), moisture (according to ASTM D 2495-87), and thermal and moisture resistance under steady-state conditions (according to ISO 11092). Moreover, surface features of treated samples were observed through SEM images. The results showed that the antibacterial treatment of fabrics with lower molecular weight (Mw) chitosan was more favorable for the finishing processes, although the whiteness of the treated samples was quite low. Additionally, cotton fabrics treated with the CA agent exhibited better hygroscopicity and vapor transmission, but tended to have more pronounced yellow color, compared to those treated with the DMDHEU agent. These physico-chemical findings clarified the bonding mechanism of cellulose–crosslinker–chitosan in antibacterial treated cotton fabrics.

Film-Forming Capability and Antibacterial Activity of Surface-Deacetylated Chitin Nanocrystals: Role of Degree of Deacetylation.

Developing sustainable food-active packaging materials is a major issue in food preservation applications. Chitin nanocrystals (ChNCs) are regarded as unique bioderived nanomaterials due to their inherent nitrogen moiety. By tuning the chemical functionality of this nanomaterial, it is possible to affect its properties, such as film-forming capability and antibacterial activity. In this work, surface-deacetylated chitin nanocrystals (D-ChNCs) with different degrees of deacetylation (DDs) were prepared by partial deacetylation of native chitin and subsequent acid hydrolysis, and their film-forming capability and antibacterial activity were studied systematically. The D-ChNCs showed favorable film-forming ability and antibacterial activity, which are closely related to their DD. With the increase in DD (from 5.7% to 45.4%), the formed transparent films based on ChNCs showed gradually increased elongation at break (from 0.5% to 2.5%) and water contact angle (from 25.5° to 87.0°), but decreased break strength (from 3.13 to 0.89 MPa), Young's modulus (from 0.84 to 0.24 MPa), and water vapor permeability (from 4.7 × 10-10 to 4.1 × 10-10g/m s Pa). Moreover, the antibacterial activity of the D-ChNCs against E. coli and S. aureus also increased with the increase of DD. This study also found that the depolarization and potential dissipation of the bacterial cell membrane induced by the contact between amino-rich D-ChNCs and bacteria through electrostatic attraction are the possible mechanisms causing bacterial cell death. This study provides a basis for understanding the effects of DD on the film-forming capability and antibacterial activity of ChNCs, which is conducive to the design of novel active packaging films based on ChNCs.