Degree Of Acetylation Research Articles

Antibacterial Activity of Chitosan Nanoparticles: A Review

In recent years, nanotechnology has attracted attention in many fields because it has several up-and-coming novel uses. Many researchers have suggested that chitosan nanoparticles (CS-NPs) and their derivatives are one of the best nanomaterials for delivering antibacterial activity. CS-NPs have a broad spectrum of antibacterial activity, but they manifest different inhibitory efficacy against gram-negative (G−) and gram-positive (G+) bacterial species. The mechanism of antibacterial action is an intricate process that varies between G− and G+ bacteria as a result of the differences in cell wall and cell membrane chemistry. In previous studies, greater antibacterial activity was more evident against G− bacteria than G+ bacteria, whereas in some studies G+ bacteria were more sensitive. Researchers predicted that the varied responses of bacteria are caused by the mixed hydrophilicity and negative charge distribution on the bacterial surface. Moreover, its activity depends on a number of variables including bacterial target (i.e., G− or G+ bacteria) and bacterial growth, as well as its concentration, pH, zeta-potential, molecular weight, and degree of acetylation. Therefore, this review examines current research on the mechanisms and factors affecting antibacterial activity, and application of CS-NPs specifically against animal and plant pathogenic bacteria.

Effect of devitalization techniques on the lipid, protein, antioxidant, and chitin fractions of black soldier fly (Hermetia illucens) larvae

The emergence of black soldier fly larvae (BSFL) as one among the vital tools for generating circular economy has enabled its use in several applications such as biorefining, valorization of waste management, treatment of industrial by-products, and bioconversion of agro-industrial residues. The ability of BSFL to assimilate chemical constituents of interest from the feed substrate and easily recover them from the insect matrix gives it a bio-reactor like characteristic. The primary unit operation after insect harvesting is the devitalization technique employed, and further processing of BSFL depends on the end application of the insect product. Conventional drying, microwave drying, scalding, blanching, microwave-assisted subcritical condition, and freezing as devitalization techniques to euthanize BSFL was executed. The impact of the devitalization techniques on the BSFL oil, protein, antioxidant, and chitin fractions was evaluated. The crude lipid yield, fatty acid profile and lipid class composition were investigated. The fatty acid profile was uniform for BSFL fractions devitalized by different techniques, and triacylglycerides were the primary lipid class in the oil fraction. The protein solubility of the defatted BSFL flour in different pH was determined. The protein quality parameters such as protein dispersibility index, urease activity index, and molecular weight distribution of the soluble protein fractions were analyzed. The frozen BSFL fraction displayed the highest protein solubility in all pH range considered, protein dispersibility index (PDI) and protein solubility (PS) was 52.86 ± 2.99% and 83.94 ± 2.96%, respectively. The aminogram of dry defatted BSFL flour, BSFL concentrate and isolate were recorded and the nitrogen-to-protein conversion (Kp) value was determined for these fractions. The antioxidant capacity of water-soluble bioactive compounds of BSFL was evaluated. Radical scavenging capacity and total polyphenol content of the BSFL fraction devitalized by microwave-assisted subcritical treatment and freezing displayed higher values when compared to other BSFL fractions. The chitin fractions were characterized by determining the degree of acetylation. Devitalization techniques strongly influence and impact the major BSFL constituents except for chitin and selection of the method should depend on the end application of the insect product. The microwave-assisted subcritical treatment proved to be an efficient devitalization technique. Whereas, freezing being a non-thermal treatment has a few limitations. Graphic abstract

Label-Free Monitoring of Histone Acetylation Using Aptamer-Functionalized Field-Effect Transistor and Quartz Crystal Microbalance Sensors.

Chemical and enzymatic modifications of amino acid residues in protein after translation contain rich information about physiological conditions and diseases. Histone acetylation/deacetylation is the essential post-translational modification by regulating gene transcription. Such qualitative changes of biomacromolecules need to be detected in point-of-care systems for an early and accurate diagnosis. However, there is no technique to aid this issue. Previously, we have applied an aptamer-functionalized field-effect transistor (FET) to the specific protein biosensing. Quantitative changes of target protein in a physiological solution have been determined by detecting innate charges of captured protein at the gate-solution interface. Moreover, we have succeeded in developing an integrated system of FET and quartz crystal microbalance (QCM) sensors for determining the adsorbed mass and charge, simultaneously or in parallel. Prompted by this, in this study, we developed a new label-free method for detecting histone acetylation using FET and QCM sensors. The loss of positive charge of lysine residue by chemically induced acetylation of histone subunits (H3 and H4) was successfully detected by potentiometric signals using anti-histone aptamer-functionalized FET. The adsorbed mass was determined by the same anti-histone aptamer-functionalized QCM. From these results, the degree of acetylation was correlated to the charge-to-mass ratio of histone subunits. The histone required for the detection was below 100 nM, owing to the high sensitivity of aptamer-functionalized FET and QCM sensors. These findings will guide us to a new way of measuring post-translational modification of protein in a decentralized manner for an early and accurate diagnosis.

Elaboration of hemicellulose-based films: Impact of the extraction process from spruce wood on the film properties

In this work, steam explosion (STEX), microwave assisted extraction (MAE) and high voltage electrical discharges (HVED) pretreatments have been evaluated for their impact on the physicochemical characteristics of extracted hemicellulosic polymers and on the resulting hemicellulose-based films. Extraction was carried out on spruce sawdust pre-soaked in water (WPS) or 1 M NaOH solution (SPS). The results have shown that STEX pretreatment gave the highest hemicellulose yields (64 and 66 mg g−1 of dry wood from WPS and SPS respectively) followed by MAE and HVED whilst MAE pretreatment produced the highest molecular mass (Mw~66 kDa of arabinoglucoronoxylans from SPS and 56 kDa for galactoglucomannans from WPS). A relatively high acetylation degree was found for STEX WPS (acetylation degree ≈ 0.35) and a high lignin content for STEX SPS (≈12%). Films have been produced by casting using sorbitol as plasticizer. Low oxygen barrier and light transmittance properties were observed for the films obtained from hemicelluloses extracted from SPS due to their high molecular mass and to intermolecular bonding of hemicelluloses and lignin.

Effect of pre-acetylation of hydroxyl functional groups by choline chloride/acetic anhydride on subsequent lignin pyrolysis

In this work, an emerging and efficient strategy for the preparation of lignin samples with different acetylation degree by choline chloride/acetic anhydride (ChCl/Aa) treatment of pine kraft lignin (PKL) is reported, and the effects of efficient pre-acetylation of hydroxyl functional groups on subsequent lignin pyrolysis are also systematically investigated. The results show that the ChCl/Aa displays a high acetylation efficiency towards the aliphatic hydroxyl (~99.1%) and phenolic hydroxyl (~94.0%) of PKL, which enhances the hydrogen to carbon effective ratio of PKL. Noticeably, the ChCl/Aa has a slight effect on β-O-4 of PKL, and the acetylation of hydroxyl is beneficial for the improvement of the maximum degradation rate of PKL. In addition, the acetylation of hydroxyl is also significantly contributed to the increment of the pyrolysis bio-oil yield. Importantly, the relative content of the H-phenols obtained from acetylated lignins pyrolysis shows a positive correlation with the acetylation degree of hydroxyl.

Evaluation of chitosan crystallinity: A high-resolution solid-state NMR spectroscopy approach

We propose a novel approach relied on high-resolution solid-state 13C NMR spectroscopy to quantify the crystallinity index of chitosans (Ch) prepared with variable average degrees of acetylation (DA¯) from 5% to 60 % and average weight molecular weight (M¯w) ranged in 0.15 × 106 g mol−1–1.2 × 106 g mol−1. The Dipolar Chemical Shift Correlation (DIPSHIFT) curve of the C(6)OH segment revealed increased mobility dynamic, which induced different distribution from trans-to-gauche conformations in relation to C(4). Indeed, 1H-13C Heteronuclear Correlation (2D HETCOR) showed that distinguished C4 chemical shifts correlates with the same aliphatic protons. The short-range ordering can be assigned to C4/C6 signals on 13C CPMAS and, for our case, the deconvolution procedure between disordered and ordered phases revealed increasing crystallinity with DA¯, as confirmed by SVD multivariate analysis. This work extended the knowledge regarding the use of 13C CPMAS technique to predict the crystallinity of chitosans without the use of amorphous standards.

Extraction, Characterization, and Utilization of Shrimp Waste Chitin Derived Chitosan in Antimicrobial Activity, Seed Germination, Preservative, and Microparticle Formulation

In this study, chitosan was obtained from the chitin of shrimp waste. It was further purified, and the degree of acetylation was measured by FTIR and NMR analysis. Further, it was subjected to antimicrobial activity against wound infection-causing bacteria and phytopathogenic fungi. It was showing good activity against both. It was used as a preservative for grape juice, where it was decreasing the turbidity. The chitosan had seed germination activity on paddy seed. Chitosan was subjected for the formation of chitosan film and subjected for antifungal activity against phytopathogenic fungi, thus used as a preservative on wrapping tomato. It was increasing the shelf life of the tomato. Chitosan was also used for microparticle formulation, where it was able to form microparticles of size about 100 µm and it possessed antifungal activity.

Acetylation of Cyclodextrin-Threaded Polyrotaxanes Yields Temperature-Responsive Phase Transition and Coacervate Formation Properties.

Stimuli-responsive materials have received considerable attention for their application in biomedical fields. Herein, the temperature-dependent phase transition behavior of acetylated polyrotaxanes (Ac-PRXs) consisting of acetylated cyclodextrins threaded onto a linear axle polymer in aqueous solution is investigated. The aqueous solutions of Ac-PRXs exhibit temperature-dependent transmittance changes when the degree of acetylation is 30-40%. Upon increasing the temperature, Ac-PRXs are dehydrated and acetyl groups are subsequently associated through hydrophobic interactions. Interestingly, the Ac-PRXs form coacervate droplets with a diameter of ≈2-3 µm above their cloud points. These temperature-responsivities of Ac-PRXs are observed for other PRXs with different axle polymer molecular weights and compositions. Consequently, the acetylation of PRXs is an attractive chemical modification for yielding temperature-responsivities, and Ac-PRXs can be applied as temperature-responsive supramolecular materials.

Extraction, Characterization, and Antimicrobial Activity of Chitosan from Horse Mussel Modiolus modiolus.

Chitin and chitosan have been proved to have enormous applications in biomedical, pharmaceutical, and industrial fields. The horse mussel, Modiolus modiolus, a refuse of the fishery industries at Thondi, is a reserve of rich chitin. The aim of this work is to extract chitosan from the horse mussel and its further characterization using Fourier transform infrared spectroscopy (FTIR), micro-Raman spectroscopy, X-ray diffraction (XRD), and elemental analysis. The result of FTIR studies revealed different functional groups of organic compounds such as out-of-plane bending (564 cm–1), C–O–C stretching (711 cm–1), and CH2 stretching (1174 cm–1) in chitosan. The degree of acetylation of the extracted chitosan was observed to be 57.43%, which makes it suitable as a biopolymer for biomedical applications. Prominent peaks observed with micro-Raman studies were at 484 cm–1 (14,264 counts/s), 2138 cm–1 (45,061 counts/s), and 2447 cm–1 (45,636 counts/s). XRD studies showed the crystalline nature of the polymer, and the maximum peak was observed at 20.04°. Elemental analysis showed a considerable decrease in the percentage of nitrogen and carbon upon the conversion of chitin to chitosan, while chitosan had a higher percentage of hydrogen and sulfur. The antibacterial activities of chitosan from the horse mussel were found to be efficient at a 200 μg/mL concentration against all the bacterial strains tested with a comparatively higher antibacterial activity against Escherichia coli (9 mm) and Bacillus subtilis (8 mm).

Nanoparticles and Colloidal Hydrogels of Chitosan-Caseinate Polyelectrolyte Complexes for Drug-Controlled Release Applications.

Chitosan–caseinate nanoparticles were synthesized by polyelectrolyte complex (PEC) formation. Caseinate is an anionic micellar nanocolloid in aqueous solutions, which association with the polycationic chitosan yielded polyelectrolyte complexes with caseinate cores surrounded by a chitosan corona. The pre-structuration of caseinate micelles facilitates the formation of natural polyelectrolyte nanoparticles with good stability and sizes around 200 nm. Such natural nanoparticles can be loaded with molecules for applications in drug-controlled release. In the nanoparticles processing, parameters such as the chitosan degree of acetylation (DA) and molecular weight, order of addition of the polyelectrolytes chitosan (polycation) and caseinate (polyanion), and added weight ratio of polycation:polyanion were varied, which were shown to influence the structure of the polyelectrolyte association, the nanoparticle size and zeta potential. Attenuated total reflection-Fourier transform infrared (ATR-FTIR) analyses revealed the chemical structure of hydrogel colloidal systems consisting of nanoparticles that contain chitosan and caseinate. Transmission electron microscopy (TEM) allowed further characterization of the spherical morphology of the nanoparticles. Furtherly, insulin was chosen as a model drug to study the application of the nanoparticles as a safe biodegradable nanocarrier system for drug-controlled release. An insulin entrapment efficiency of 75% was achieved in the chitosan-caseinate nanoparticles.

Suppressed crystallization and enhanced gas permeability in thin films of cellulose acetate blends

Film thickness and blending can affect crystallization and chain dynamics of semi-crystalline polymers, particularly for submicron films. Herein we apply these insights to elucidate a long-standing puzzle for industrial asymmetric membranes for CO2 removal from natural gas, which are based on blends of cellulose diacetate (CDA with a degree of acetylation or DS of 2.45) and cellulose triacetate (CTA with a DS of 2.87). The asymmetric membranes comprise thin selective layers (~100 nm) and have been reported to exhibit gas permeability much higher than the bulk blends. We hypothesize that the film thickness and blending confine crystallization and decrease the crystallinity, increasing gas permeability while retaining high selectivity. Specifically, we systematically determined crystallinity for CTA and two blends with various thicknesses ranging from ≈500 nm to ≈20 μm. Adding 75 mass% CTA in CDA (CDA-CTA75) decreases the crystallinity from 34 vol% to 23 vol% at ≈ 20 μm (accompanied by CO2 permeability increase from 3.9 Barrer to 7.1 Barrer), while decreasing the film thickness of CDA-CTA75 from ≈20 μm to ≈ 1.0 μm decreases the crystallinity from 23 vol% to 13 vol% and increases CO2 permeability from 7.1 Barrer to 14 Barrer. Understanding polymer chain dynamics and crystallization in thin films can be instrumental in designing high-performance membranes for industrial gas separations.

Compatibility improvement of poly(lactic acid)/thermoplastic starch blown films using acetylated starch

AbstractThe present research aims to improve the compatibility between relatively hydrophobic poly(lactic acid) (PLA) and hydrophilic thermoplastic starch (TPS) and the properties of the PLA/TPS blends by replacing TPS from native cassava starch (TPSN) with TPS from acetylated starch (TPSA). The effects of the degree of acetylation (DA) of acetylated starch, that is, 0.021, 0.031, and 0.074, on the morphological characteristics and properties of PLA/TPS blend are investigated. The melt blends of PLA and TPS with a weight proportion of PLA:TPS of 50:50 are fabricated and then blown into films. Scanning electron microscopy confirms the dispersion of TPS phase in the PLA matrix. Better dispersion and smaller size of the TPS phase are observed for the PLA/TPSA blend films with low DA of acetylated starch, resulting in improved tensile and barrier properties and increased storage modulus, thermal stability, and Tg, Tcc, and Tm of PLA. Elongation at break of the PLA/TPSA blend increases up to 57%, whereas its water vapor permeability and oxygen permeability decrease about 15%. The obtained PLA/TPSA blend films have the potential to be applied as biodegradable flexible packaging.

Comparative Characterization of Aspergillus Pectin Lyases by Discriminative Substrate Degradation Profiling.

Fungal genomes often contain several copies of genes that encode carbohydrate active enzymes having similar activity. The copies usually have slight sequence variability, and it has been suggested that the multigenecity represents distinct reaction optima versions of the enzyme. Whether the copies represent differences in substrate attack proficiencies of the enzyme have rarely been considered. The genomes of Aspergillus species encode several pectin lyases (EC 4.2.2.10), which all belong to polysaccharide lyase subfamily PL1_4 in the CAZy database. The enzymes differ in terms of sequence identity and phylogeny, and exhibit structural differences near the active site in their homology models. These enzymes catalyze pectin degradation via eliminative cleavage of the α-(1,4) glycosidic linkages in homogalacturonan with a preference for linkages between methyl-esterified galacturonate residues. This study examines four different pectin lyases (PelB, PelC, PelD, and PelF) encoded by the same Aspergillus sp. (namely A. luchuensis), and further compares two PelA pectin lyases from two related Aspergillus spp. (A. aculeatus and A. tubingensis). We report the phylogeny, enzyme kinetics, and enzymatic degradation profiles of the enzymes’ action on apple pectin, citrus pectin, and sugar beet pectin. All the pectin lyases exerted highest reaction rate on apple pectin [degree of methoxylation (DM) 69%, degree of acetylation (DAc) 2%] and lowest reaction rate on sugar beet pectin (DM 56%, DAc 19%). Activity comparison at pH 5–5.5 produced the following ranking: PelB > PelA > PelD > PelF > PelC. The evolution of homogalacturonan-oligomer product profiles during reaction was analyzed by liquid chromatography with mass spectrometry (LC-MS) detection. This analyses revealed subtle differences in the product profiles indicating distinct substrate degradation preferences amongst the enzymes, notably with regard to acetyl substitutions. The LC-MS product profiling analysis thus disclosed that the multigenecity appears to provide the fungus with additional substrate degradation versatility. This product profiling furthermore represents a novel approach to functionally compare pectin-degrading enzymes, which can help explain structure-function relations and reaction properties of disparate copies of carbohydrate active enzymes. A better understanding of the product profiles generated by pectin modifying enzymes has significant implications for targeted pectin modification in food and biorefinery processes.

Comparative study on glucomannans with different structural characteristics: Functional properties and intestinal production of short chain fatty acids

Glucomannans (GMs) from abundant natural resources have excellent processing properties and plentiful bioactivities. In current study, functional properties of GMs with different structural characteristics, including KGM from konjac, DOP from dendrobium, AGP40, ASP-4N, ASP-6N, & ASP-8N from aloe were determined. Results suggested that molecular weights (Mw) of GMs were positively correlated with their water absorption capacity, fat absorption capacity, and viscosity, while ratio of mannose/glucose showed negative effect. Higher degree of acetylation (DA) mainly corresponded to higher values of solubility and ζ-potential. Then, effects of the six GMs on general health status, serum biochemicals, and intestinal SCFAs production in mice were evaluated in vivo. Analysis of general health status and levels of serum biochemicals revealed that mice with consecutive supplementation of GMs for 14 days performed normally compared with those in control group. Interestingly, the productions of SCFAs (mainly acetate and butyrate) in the cecal and colonic contents were significantly promoted. Generally, higher concentrations of SCFAs were produced when mice were treated with GMs having higher Mw, ratio of glucose, and DA. The current investigation suggested that both functional and intestinal fermentation property of GMs were jointly determined by the monosaccharide composition, molecular weight, and degree of acetylation.

Green, Simple, and Effective Process for the Comprehensive Utilization of Shrimp Shell Waste.

An environmentally friendly approach for the comprehensive utilization of shrimp shell waste was reported. Instant catapult steam explosion (ICSE) was employed for shrimp shell waste pretreatment. After ICSE, lower crystallinity and greater surface areas of shrimp shells were achieved, which significantly enhanced the extraction of chitin. Compared to the traditional method, weaker organic acid (HCOOH) and much lower dosages of KOH (90% molar less) were used, and chitin with a high demineralization rate (98.2%) and deproteinization rate (97.7%) was obtained. The wastewater was neutralized by simply intermixing, and it was recycled as a potential plant fertilizer because it contained more oligopeptides, calcium, and potassium, but it was less salty and therefore non-toxic to plants. The whole process produced less solid waste and no waste water. The obtained chitin also showed a low degree of acetylation (50.5%), which demonstrates the potential for environmentally friendly preparation of chitosan in dilute alkali through ICSE.

Acetylation of tropical hardwood species from forest plantations in Costa Rica: an FTIR spectroscopic analysis

Acetylation of softwoods has been largely investigated to increase the dimensional stability and biological resistance of wood. However, the knowledge of this technology has not been applied to tropical hardwood species up to date. The objective of this work was to study the effect of acetylation on nine tropical hardwood species, from forest plantations in Costa Rica, by applying acetic anhydride in three different treatment times (1 h, 2.5 h, 4 h), as well as to evaluate this by Fourier-Transform Infrared Spectroscopy (FTIR). Results showed that weight percentage gain (WPG) of wood varied from 2.2 to 16.8%, with Vochysia ferruginea species showing the highest WPG, and Gmelina arborea and Tectona grandis species exhibiting the lowest WPGs. Tropical woods such as Enterolobium cyclocarpum, Hieronyma alchorneoides and Samanea saman exhibited statistical differences among treatment times, whereas the rest of the species studied showed no significant differences. In general, the most effective acetylation time was 2.5 h for all the species. The ratio of intensity (RI) from the FTIR spectra was greater at the 1732 cm−1, 1372 cm−1 and 1228 cm−1 peaks for all tropical species, associated with lignin. A good correlation between the RI of those peaks and WPG was found; the same was also found between all RIs and each other. Meanwhile, RI associated to the hemicelluloses and lignin (1592 cm−1 and 1034 cm−1 peaks, respectively) showed no correlation with WPG, nor between each other or with the other RIs. Furthermore, it was suggested that RI at 1732 cm−1 (associated to acetyl groups C=O) can be considered as a reliable indicator of the degree of acetylation for tropical hardwood species. Finally, it was observed that tropical hardwoods having more suitable anatomical features, like larger vessel diameter, higher ray width and frequency, and lesser deposits such as gums and tyloses in the vessels, resulted in significantly higher WPGs.

Comprehensive liamocin biosurfactants analysis by reversed phase liquid chromatography coupled to mass spectrometric and charged-aerosol detection.

Liamocin biosurfactants and structurally related exophilins secreted by the Aureobasidium pullulans (A. pullulans) strain NRRL62031 were firstly analyzed by hyphenation of high-performance liquid chromatography (HPLC) with high-resolution mass spectrometry (HRMS). Ten different analytes were detected and identified by their accurate masses and divided into subclasses according to their different head groups: three liamocins with arabitol as head group, three mannitol liamocins, and four exophilins. A baseline separation of congeners within the subclasses was achieved by reversed phase HPLC on a C18 stationary phase, whereas an overlap of subclasses occurred. The structures were simultaneously confirmed by online tandem mass spectrometry (MS/MS) experiments in positive and negative ionization mode. The assigned polyol head groups and thus the feasibility of this method were confirmed by gas chromatography (GC)-MS data obtained after hydrolysis and derivatization of the liamocins. Based on the varying structural characteristics of liamocins, e.g. the polyol head group (or even none for exophilins) and the degree of acetylation, different detector response in LC-MS was expected, impairing relative quantification of congeners. Therefore, a complementary quantification method was developed using HPLC coupled to charged-aerosol detection (CAD), which allows the determination of the amount of the individual liamocin species without authentic liamocin standards. Hence, the here presented hyphenated techniques facilitate comprehensive analysis of liamocin biosurfactants.

Hyperspectral Near-Infrared Image Assessment of Surface-Acetylated Solid Wood.

Visualization of acetic anhydride flow and its heterogeneity within the wood block necessitates the development of a reliable and robust analytical method. Hyperspectral imaging has the potential to acquire a continuous spectrum of chemical analytes at different spectral channels in terms of pixels. The large set of chemical data (3-dimensional) can be expanded into relevant information in a multivariate fashion. We quantified gradients in acetylation degree over cross sections of Scots pine sapwood caused by a one-sided flow of acetic anhydride into wood blocks using near-infrared hyperspectral imaging. A principal component analysis (PCA) model was used to decompose the high-dimensional data into orthogonal components. Moreover, a partial least-squares (PLS) hyperspectral image regression model was developed to quantify heterogeneity in acetylation degree that was affected by the flow of acetic anhydride through wood blocks and into the tracheid cell walls. The model was validated and optimized with an external test data set and a prediction map using the root-mean-squared error of an individual predicted pixel. The model performance parameters are well suited, and prediction of the acetylation degree at the image level was complemented with confocal Raman imaging of selected areas on the microlevel. NIR image regression showed that the acetylation degree was determined not only by the time-dependent flow of the acetic anhydride through the wood macropores but also by the diffusion of the anhydride into the wood cell walls. Thereby, thin-walled earlywood sections were acetylated faster than the thick-walled latewood sections. Our results demonstrate the suitability of near-infrared imaging as a tool for quality control and process optimization at the industrial scale.

Regression and mathematical modeling of fluoride ion adsorption from contaminated water using a magnetic versatile biomaterial & chelating agent: Insight on production & experimental approaches, mechanism and effects of potential interferers

Fluoride is one of the chemicals that enter the human body through drinking water and, at higher concentrations, can cause various long-term health effects. Owing to remove the pollutant from aqueous solutions on large-scale, researchers are always exploring efficient, inexpensive, and easily recoverable adsorbents. In this research study, a versatile magnetic biomaterial & chelating agent (Chitosan) is used as an adsorbent for fluoride removal. In the present research, chitin was extracted from discarded shrimp shells. The obtained Chitosan was characterized based on its yielding, moisture and ash content, degree of acetylation and water binding capacity according to standard protocols. Also, in this study, differential evolution optimization is used to evaluate isotherm and kinetic model parameters using nonlinear model expressions, thus depicting inherent mechanisms. The isotherm and kinetic studies revealed that the adsorption process follows Langmuir and the pseudo 2nd order kinetic model. The interactive effect of process variables is investigated, and their optimal conditions for higher removal efficiency are estimated using response surface methodology. A quadratic model was used to predict removal efficiency at different operating conditions, which resulted in R2 of 0.9949. Optimum adsorption efficiency (93.1%) was observed at an adsorbent rate of 1 g/L, initial concentration of 1 mg/L, pH of 3, and contact time of 25 min. The thermodynamic study is indicating that the process is exothermic and spontaneous. The effect of interventions such as chloride, acidic, and sulfate on fluoride removal was also investigated, and results indicated that Chitosan-Fe3O4 is also efficient in their presence. A hybrid model of ANN and GA predicted the fluoride removal at different operating conditions, and results indicated that prediction values result in R2 of 0.9825. Thus, these results confirm the remarkable ability of Chitosan-Fe3O4 nanocomposite for fluoride removal.

Production, characterization, and biological activity of a chitin-like EPS produced by Mortierella alpina under submerged fermentation

The production of a chitin-like exopolysaccharide (EPS) was optimized through experimental design methods, evaluating the influence of urea, phosphate, and glucose. Under optimized conditions, up to 1.51 g/L was produced and its physicochemical characteristics were evaluated by chromatography, NMR, and FTIR spectroscopy, and rheological techniques. The results showed a homogeneous EPS (Mw 4.9 × 105 g mol−1) composed of chitin, linear polymer of β-(1→4)-linked N-acetyl-d-glucosamine residues. The acetylation degree as determined by 13C CP-MAS NMR spectroscopy was over 90 %. The EPS biological activities, such as antioxidant effect and antitumor properties, were evaluated. To the best of our knowledge, this is the first study on the production of a new alternative of extracellular chitin-like polysaccharide with promising bioactive properties from the filamentous fungus M. alpina.