Physicochemical characterization of chitin extracted by different treatment sequences from an edible insect.

Chitin present in the shell of edible insects is a potential source of chitin, lipids, and proteins, and it exerts various biological activities. Thus far, only a few studies have focused on the use of chitin as a source of high-protein-diet oligosaccharides. The use of insect chitin for the production of high-protein-diet oligosaccharides can lessen the reliance on diet crops. Moreover, although chitin composition in Tenebrio molitor larva, pupa, and adult has been extensively investigated, chitin extraction from T. molitor larval whole body and exuvium has received poor attention. The present study compared the effectiveness of two techniques for extracting high-protein-diet chitin oligosaccharide from an edible insect (T. molitor). Two different extraction sequences of chitin from the larval stage (molitor stage larvae) and adult stage (molitor stage adult) of edible T. molitor were investigated. Two processing steps were employed: (a) deproteinization (DEP) and (b) demineralization (DEM) treatments. Differences in the order, conditions, and period of their application resulted in two different chitin extraction procedures. The viscosity, degree of polymerization, and crystallinity index of the chitin extracted using the two procedures were measured, and its chemical components (chitin, ash, protein, fat, and moisture contents) were determined. T. molitor adults and larvae treated sequentially with DEM-DEP demonstrated the greatest yield of approximately 14.62 % ± 0.15 and 6.096 % ± 0.10 %, respectively. By contrast, when treated sequentially with DEP-DEM, the recorded yields were 10.96 % ± 0.18 and 5.31 % ± 0.38, respectively. Differences in the degree of deacetylation between both methods were observed. Additionally, Fourier transform infrared spectroscopy and X-ray diffractometry of the extracted chitin along with a commercial sample revealed consistent chain conformation, mean hydrogen bonding, and crystallinity index. In this way, residues produced by farmed edible insects can be recovered and used as a novel source of chitin.

Laser-induced porous graphene electrodes from polyketimine membranes for paracetamol sensing.

The development of cost-effective materials for fabricating electrodes is crucial for drug, pharmaceutical and environmental applications. This paper presents the synthesis and characterization of a novel polyketimine (PKI) membrane obtained by condensing partially of different weight percentages of oxidized polyvinyl alcohol and aminated polyether sulfone. Using the PKI membrane as a scaffold, we introduced laser-induced graphene electrodes (LIGEs) for the efficient electrochemical sensing of paracetamol (PCM), which serves as a model drug. Electrochemical measurements were conducted to assess the physico-chemical properties, including laser-induced porous graphene features, such as the heterogeneous electron transfer (HET) rate and electrochemically active surface area (ECSA). The obtained results demonstrate that the LIGEs exhibit excellent performance in PCM sensing, showing a linear detection range of 50-600 µM with a detection limit (LOD) as low as 14.3 µM and a good selectivity toward uric acid. Furthermore, the functionalization of the electrode surface with AuNPs improved the electrode physico-chemical properties (HET and ECSA) and lowered the detection limit down to 1.1 µM. Consequently, these affordable electrodes hold great potential for analysing other drugs and detecting heavy metal cations in various applications.

Synthesis and evaluation of N-allylthiourea-modified chitosan for adsorptive removal of arsenazo III dye from aqueous solutions.

N-allylthiourea chitosan (ATUCS), a chelating material, was prepared, characterized, and studied for the removal of arsenazo III (As (III)) dye from aqueous solution. Scanning electron microscopy (SEM), energy-dispersive X-ray (EDX), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), and 1H- and 13C-nuclear magnetic resonance (NMR) were used to characterize the prepared adsorbent and to investigate the adsorption mechanism. Furthermore, the adsorption behavior of chitosan (CS) and ATUCS were studied under various conditions. The equilibrium adsorbed amount of As (III) onto ATUCS was found to be 116.3 mg/g, compared to 87.3 mg/g with respect to CS. The regeneration of the loaded CS and ATUCS were studied using 1:1 solution of H2O2-H2SO4 and reused with certain change in efficiency after the third cycle. The adsorption process was found to fit well with pseudo-second-order kinetic model. The equilibrium data were better described with the Freundlich isotherm. The monolayer adsorption capacity was found to be 204.08 and 90.90 mg/g for the As (III)/ATUCS and As (III)/CS systems, respectively, at 25 °C. The pH of the higher uptake of As (III) onto ATUCS and CS was 4-5 and 8.0, respectively. The results demonstrated improved adsorption of As (III) using ATUCS as compared to the CS.

Mercerization effect on structure and electrical properties of cellulose: Development of a novel fast Na-ionic conductor.

Mercerized cellulose (alkali cellulose C6H10O5* NaOH) was obtained by treatment of cotton linters (cellulose) with aqueous sodium hydroxide. Cellulose and alkali-cellulose samples with relative density of 78% and 79% were obtained after sintering the material in air at optimal sintering temperatures of 423 K and 473 K, respectively. The electrical properties of the samples were studied by impedance spectroscopy in the frequency range from 13 MHz to 50 Hz at temperatures between 393 K and 493 K. The influence of cellulose mercerization on electrical properties of cotton linters was observed. The cellulose behaves like an electrical insulator. Contrariwise, the alkali-cellulose is a fast-ionic conductor with a conductivity value of σ473 K = 3.22 × 10-6 S cm-1 having activation energies of 0.49 eV and 0.68 eV at temperature range of 393 K-458 K and 459 K-500 K, respectively. The change of activation energy value has been discussed in relation to thermal stability.

An unexpected reactivity during periodate oxidation of chitosan and the affinity of its 2, 3-di-aldehyde toward sulfa drugs.

In an attempt to determine the reactivity during the periodate oxidation of the vicinal amino sugar, chitosan was oxidized by KIO4 in a neutral medium. The reactivity was unexpectedly found to be low. The formation of di-aldehyde chitosan (DACT) might cause the low reactivity of chitosan oxidation. Therefore, density functional theory (DFT) calculations were carried out, which revealed that the greater stability of the cyclic amino iodate intermediate might retard the ring opening to form DACT. Furthermore, the affinity of the formation of two novel Schiff bases from the interaction of delivered DACT with two sulfa drugs [sulfanilamide and sulfathiazole] was also investigated using aldehyde content estimation. DACT and Schiff's bases were characterized by FT-IR spectroscopy, X-ray diffraction, and DTA analysis. The X-ray diffraction plane (110) of DACT at the high angle side was expanded more by sulfathiazole than sulfanilamide, indicating that sulfathiazole reacted effectively with DACT. The lowest interaction of DACT with sulfa drugs could be ascribed to the lowest aldehyde content and the intramolecular hemiacetal formation that hinders the Schiff's base condensation.

Peculiar behavior of starch 2,3-dialdehyde towards sulfanilamide and sulfathiazole.

In this study, starch (1) was oxidized to starch-2,3-dialdehyde (DAS; 2) using potassium periodate. In addition, two novel Schiff's bases (5 &6) were synthesized via a condensation reaction between DAS (2) and sulfa drugs (sulfanilamide; 3 & sulfathiazole; 4). The synthesized Schiff's bases (5 &6) were characterized by FT-IR spectroscopy, X-ray diffraction and DSC analysis. DAS can easily be oxidized owing to its high aldehyde content (91.0%). However, it has low reactivity towards sulfanilamide (3) and sulfathiazole (4). According to the diffraction functional theory, this peculiar behavior is caused by the absence of V-shape in α-glucan linkage in DAS molecules, making the carbonyl group least electropositive. This reduces the nucleophilic attacks of the amino group in sulfa drugs towards the carbonyl group in DAS.

Enhancing biocompatibility of some cation selective electrodes using heparin modified bacterial cellulose.

Bacterial cellulose (BC) and heparin-modified bacterial cellulose (HBC) were utilized to enhance the biocompatibility of highly thrombogenic PVC-based potassium and calcium membrane electrodes. Three types of membrane electrodes were prepared: (1) conventional PVC electrode (control), (2) PVC-based electrode sandwiched with bacterial cellulose membrane (BC-PVC), and (3) PVC-based electrode sandwiched with heparin-modified bacterial cellulose membrane (HBC-PVC). The potentiometric response characteristics of the modified potassium and calcium membrane electrodes (BC-PVC and HBC-PVC) were compared with those of the control PVC-based potassium and calcium selective electrode, respectively. Response characteristics of the modified membrane electrodes were comparable to the control PVC membrane electrode. The platelet adhesion investigations indicated that (BC) and (HBC) layers are less thrombogenic compared to PVC. Therefore, use of BC or HBC would enable the enhancement of the biocompatibility of PVC-based membrane electrodes for potassium and calcium while practically maintaining the overall electrochemical performance of the PVC sensing film.

Physicochemical characterization of novel Schiff bases derived from developed bacterial cellulose 2,3-dialdehyde.

The synthesis of two novel Schiff's bases (cellulose-2,3-bis-[(4-methylene-amino)-benzene-sulfonamide] (5) & cellulose-2,3-bis-[(4-methylene-amino)-N-(thiazol-2-yl)-benzenesulfonamide] (6) via condensation reactions of periodate oxidized developed bacterial cellulose ODBC (2) with sulfa drugs [sulfanilamide (3) & sulfathiazole (4)] was reported. The physicochemical characterization of the condensation products was performed using FTIR, (1)H NMR, (13)C NMR spectral analyses, X-ray diffraction and DTA. The ODBC exhibited the highest degree of oxidation based on the aldehyde group number percentage (82.9%), which confirms the highest reactivity of developed bacterial cellulose [DBC (1)]. The X-ray diffractograms indicated an increase in the interplanar distance of the cellulose Schiff base (6) compared to ODBC (2) due to sulfathiazole (4) inclusion between ODBC (2) sheets corresponding to the 1 1 0 plane. In addition, the aldehyde content of Schiff base (6) was (20.8%) much lower than that of Schiff base (5) (41.5%). These results confirmed the high affinity of sulfathiazole (4) to the ODBC (2) chain, and the substantial changes in the original properties of ODBC were due to these chemical modifications rather than the sulfanilamide (3).

Effect of different alkaline solutions on crystalline structure of cellulose at different temperatures.

Effect of alkaline solutions such as 10% NaOH, NaOH/urea and NaOH/ethylene glycol solutions on crystalline structure of different cellulosic fibers (cotton linter and filter paper) was investigated at room temperature and -4°C. The highest dissolution of cotton linter and filter paper was observed in NaOH/ethylene glycol at both temperatures. X-ray patterns of treated cotton linter with different alkaline solutions at low temperature showed only two diffractions at 2θ=12.5° and 21.0°, which belonged to the crystalline structure of cellulose II. CP/MAS (13)C NMR spectra showed the doublet peaks at 89.2 ppm and 88.3 ppm representing C4 resonance for cellulose I at room temperature, Whereas, at low temperature the doublet peaks were observed at 89.2 ppm and 87.8 ppm representing C4 resonance for cellulose II. Degree of polymerization of cellulose plays an important role in cellulose dissolution in different alkaline solutions and temperatures, where, a low temperature gives high dissolutions percentage with change in crystalline structure from cellulose I to cellulose II forms.

Vitamin C enhances bacterial cellulose production in Gluconacetobacter xylinus.

Influence of vitamin C (ascorbic acid) on bacterial cellulose (BC) production and crystal structure was studied using four strains of Gluconacetobacter xylinus (ATCC 10245, IFO 13693, 13772 and 13773). BC productivity of all strains was increased in presence of vitamin C (0.5% w/w), the average BC production reached 0.47 g/30 ml compared with 0.25 g/30 ml without vitamin C. Enhanced productivity is associated with a decrease in gluconic acid concentration that is produced from Gluconacetobacter xylinus during BC production. X-ray results showed that the crystallinity index of BC produced in presence of ascorbic acid was the lowest with remarkable change in d-spacing. These results were confirmed by using solid state (13)CNMR. The increase in BC yield in presence of vitamin C is due to its antioxidant behavior and confirms our past work on lignosulfonate influence on BC.