Optimum parameters for production of chitin and chitosan from squilla (S. empusa)

Chitin and chitosan of high quality were produced from squilla, a by‐catch of Indian Ocean fisheries, by demineralization, deproteination, and deacetylation. Optimum conditions for the production of chitin and chitosan were determined. The quality of chitin was assessed from its ash and protein content. Ash content was below 1% after treatment with 4% HCl for 12 h at 50°C. A protein content of less than 1% could be achieved by treatment with 4% NaOH in 12 h but only at a temperature of 70°C or higher. Production of chitin was also tested by a three‐stage treatment with altering sequence of sodium hydroxide and hydrochloric acid (HCl–NaOH–HCl or NaOH–HCl–NaOH). This three‐step treatment appeared to be successful to achieve a mineral content and protein content below 1% within 30 h and at a temperature not exceeding 50°C. The chitin obtained under optimum conditions was tested for deacetylation using NaOH concentrations of 40 and 50% for 12–44 h at 30, 50 and 70°C. The chitosan obtained had a degree of deacetylation of 77–86%, a viscosity of 8.2–16.2 × 10² cps, solubility of 98%, and molecular weight of ? 1 × 10⁶ dalton. The data show that processing of squilla waste can lead to a high quality chitosan, useful for a broad range of applications. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 103: 3694–3700, 2007     

Liquid‐crystalline behavior of chitosan in malic acid

This report describes how the degree of deacetylation and molecular weight of chitosan and the concentrations of sodium chloride and malic acid affect the formation of lyotropic chitosan liquid crystals. Chitosan samples of various degrees of deacetylation were prepared from β‐chitin that was isolated from squid pens. They were degraded by ultrasonic irradiation to various molecular weights. The critical concentrations forming chitosan liquid crystals were determined with a polarized microscope. A chitosan sample with a degree of deacetylation of 67.2–83.6% formed cholesteric lyotropic liquid crystals when it was dissolved in 0.37–2.59M malic acid. The critical concentrations increased with increasing degrees of deacetylation of chitosan. They decreased with increasing molecular weights or increasing concentrations of sodium chloride and malic acid. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007     

Electrospinning of chitosan/PVA nanofibrous membrane at ultralow solvent concentration

In this work, chitin flakes were deacetylated with 50% (w/v) sodium hydroxide under nitrogen atmosphere at 120 °C for 80 min to obtain chitosan. The chitosan produced was characterized for degree of deacetylation (DD) and molecular weight. Chitosan with the DD of 78–80% was reproducibly obtained. Molecular weight showed an inverse relationship with concentration of NaOH. Chitosan nanofibrous membrane was prepared via the electrospinning of chitosan/polyvinyl alcohol (CH/PVA) aqueous solutions with varying blend compositions. The characteristics of CH/PVA nanofibrous membranes were studied as a function of viscosity of solution and applied voltage. A uniform nanofibrous membrane of average fibre diameter of 80–300 nm was obtained with blend of 2% (w/v) chitosan solution in 1% (v/v) acetic acid and 5% (w/v) PVA in distilled water in the electric field of 20–25 kV with varying proportion of CH/PVA. With the CH/PVA mass ratios; 40/60 to 10/90, electrospinning of nanofibres could be done. The electrospun nanofibrous membrane was analyzed by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Thermo gravimetric analysis (TGA). SEM images showed that the morphology and diameter of the nanofibres were mainly affected by the weight ratio of CH/PVA. XRD and FTIR confirmed the strong intermolecular hydrogen bonding between the molecules of Chitosan and PVA.     

Chitin characterization by SEM,FTIR, XRD,and 13C cross polarization/mass angle spinning NMR

The full characterization of chitin obtained from squid, shrimp, prawn, lobsters, and king crab is reported. Elemental analysis, including metals such as Ca, Mg, Zn, Cd, Hg, Cr, Mn, Cu, and Pb, was performed, which is quite relevant because the skeleton composition is slightly different for each species. The morphology was studied by means of TEM and their compositions were determined by energy‐dispersive X‐ray analysis. ¹³C cross polarization/magic angle spinning NMR was applied to determine the chemical shift of all the carbons and the difference between them. Chitin was isolated by using chemical methods, alternating hydrochloric acid and sodium hydroxide. The α‐chitin from shrimp, prawn, lobsters, and king crabs showed two signals at 73.7 and 75.6 ppm. Meanwhile, the β‐chitin from squid exhibited one signal at 75.2 ppm. FTIR studies were used to analyze α‐chitin from shrimp and β‐chitin from squid. The α‐chitin exhibited amide I vibration modes at 1660 and 1627 cm^?1, whereas the β‐chitin showed one band at 1656 cm^?1. X‐ray diffraction showed that α‐chitin is orthorhombic (a = 4.74 Å, b = 18.86 Å, and c = 10.32 Å) and β‐chitin had a monoclinic dihydrated form (a = 4.80 Å, b = 10.40 Å, c = 11.10 Å, and β = 97°). © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 1876–1885, 2004     

Evaluation of molar weight and deacetylation degree of chitosan during chitin deacetylation reaction: Used to produce biofilm

Chitosan is a polysaccharide derived from chitin, mainly of crustacean shells and shrimp wastes. The utilization of chitosan is related to the molar weight and deacetylation degree of the biopolymer. The aim of this work is to study the chitin deacetylation reaction, by the viscosity average molar weight and deacetylation degree of chitosan as a function of reaction time. Deacetylation was carried out in concentrated alkaline solution, 421 g L⁻¹, at 130 °C and the reaction occurred during 4 h. Chitosan paste obtained after 20, 90 and 240 min was used to produce biofilms, which were characterized according water vapor permeability and mechanical properties (tensile strength and percentage tensile elongation at break). During the reaction time deacetylation degree reached 93%, and a 50% reduction in the viscosity average molar weight value in relation to the value of the first 20 min of reaction was found Both reactions presented a kinetic behavior of the pseudo-first order. Biofilm produced from the paste of chitosan with high deacetylation degree showed higher water vapor permeability (WVP), tensile strength (TS) and elongation (E) when compared to films with a low deacetylation.     

Chitin production by Lactobacillus fermentation of shrimp biowaste in a drum reactor and its chemical conversion to chitosan

Chitin was produced by fermenting shrimp heads and shells with Lactobacillus plantarum 541 in a drum reactor with an internal volume of 3 dm 3 . The crude chitin yield from heads and shells was 4.5 and 13% respectively, comparable to the values obtained by the chemical method. For shrimp heads 83% deproteination and 88% demineralisation and for shrimp shells 66% deproteination and 63% demineralisation were achieved. The liquor obtained in both cases was of good sensory quality with a high content of essential amino acids and therefore with potential to produce protein powder for human consumption. The crude chitin was refined and converted to chitosan using 12.5 M NaOH. The chitosan obtained had a residual ash and protein content below 1%, a solubility of more than 98%, a viscosity in the range 50–400 cP and a degree of deacetylation of 81–84%. The molecular weight was in the range (0.8–1.4) × 10⁶ Da. IR analysis indicated that the chitosan obtained through fermentation was similar to that obtained by the chemical method. Copyright © 2005 Society of Chemical Industry     

Contribution to the preparation of chitins and chitosans with controlled physico-chemical properties

In this paper, from many new examples, our approach on the preparation of chitins and chitosans with controlled physico-chemical characteristics was presented. The chitosan samples were prepared from -chitin from crustacean shells and β-chitin from squid pens. The chitin deacetylation was carried out according to two methods using, respectively, as alkaline agent, the aqueous sodium hydroxide solution and anhydrous potassium hydroxide. The role of the source and of the process on the N-deacetylation reactions is confirmed. The effect of the addition of sodium borohydride or thiophenol within the reaction medium was studied. One of the parameters conditioning the physico-chemical characteristics of chitosan being in relation with the nature and the quality of original chitin, the role of this parameter was examined and the isolation process was discussed to put in evidence its advantages compared to other processes quoted in the literature by relying on new results.     

Chitin and chitosan nanofibers: electrospinning of chitin and deacetylation of chitin nanofibers

An electrospinning method was used to fabricate chitin nanofibous matrix for wound dressings. Chitin was depolymerized by gamma irradiation to improve its solubility. The electrospinning of chitin was performed with 1,1,1,3,3,3-hexafluoro-2-propanol (HFIP) as a spinning solvent. Morphology of as-spun and deacetylated chitin (chitosan) nanofibers was investigated by scanning electron microscopy. Although as-spun chitin nanofibers had the broad fiber diameter distribution, most of the fiber diameters are less than 100 nm. From the image analysis, they had an average diameter of 110 nm and their diameters ranged from 40 to 640 nm. For deacetylation, as-spun chitin nanofibous matrix was chemically treated with a 40% aqueous NaOH solution at 60 or 100 °C. With the deacetylation for 150 min at 100 °C or for 1day at 60 °C, chitin matrix was transformed into chitosan matrix with degree of deacetylation (DD) ∼85% without dimensional change (shrinkage). This structural transformation from chitin to chitosan was confirmed by FT-IR and WAXD.     

Valorization of chitins extracted from North Morocco shrimps: Comparison of chitin reactivity and characteristics

Huge quantities of waste discharged by the gray and pink shrimp decortication units in the North of Morocco can be valorized by producing about 950 tons of pure chitin, which can be transformed into 700 tons of highly to totally deacetylated chitosan. During the preparation of chitin and chitosan from gray and pink shrimps, differences in reaction behavior were observed even though these are taxonomically close species. The presented results concern several chitinous sources, and they show that the progress in the N-deacetylation reactions of chitin would be linked to the crystallinity index of the starting chitin. Following the kinetic study of the polymer hydrolysis during N-deacetylation, the difference in the molecular weights of the chitosan samples obtained under identical reaction conditions was related to the differences between molecular weights of the native chitin, 478 000 g.mol⁻¹ for pink shrimp and 562 000 for gray shrimp. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019 , 136, 47804.     

Study of the influence of processing parameters on the production of carboxymethylchitin

Carboxymethylchitin was prepared at different reaction temperatures and from alkali chitin with different concentrations of alkali. Properties of the product were studied. Alkali chitin were prepared using freshly prepared sodium hydroxide of 45, 50, 55, 60 and 65% (w/w) concentration and carboxymethylated using monochloroacetic acid at controlled (35-40 °C) and uncontrolled (30-80 °C) temperature conditions. Molecular weight, viscosity, degree of deacetylation, etc. of the resultant product, i.e. carboxymethylchitin were determined. It was found that the reaction temperature has a profound influence on the property of the product than alkali concentration. A hygroscopic and completely water-soluble product was formed. Optimum conditions for the production of carboxymethylchitin were found to be 60% NaOH concentration and at 35-40 °C reaction temperature. At these conditions, it was obtained with a molecular weight of 4.11×10⁶ Da, viscosity 1926 cP and degree of deacetylation 45.02%.     

Chitosan from Muga silkworms (Antheraea assamensis) and its influence on thermal degradation behavior of poly(lactic acid) based biocomposite films

The research work is focused on extraction of chitin from Muga silkworms (MS) and its conversion into chitosan by chemical treatment process. The extracted amount of chitin and chitosan from MS were obtained ～8 wt % and ～7 wt %, respectively. Potentiometric titrations, conductometric titrations, elemental analysis, ¹H‐NMR and FTIR analyses were employed to calculate the degree of deacetylation of chitosan (extracted at 80 ºC after 10 h) and found as 77% ± 2, 81% ± 1.8, 82% ± 2.4, 97.77% ± 0.3, and 82% ± 1.8, respectively. The deacetylation process of chitin showed pseudo‐first order reaction kinetics and activation energy was estimated as ～15.5 kJ/mole. The extracted chitosan (at 80 ºC after 10 h) showed higher crystallinity and improved thermal stability with respect to chitosan extracted from other marine sources. Subsequently, poly(lactic acid) (PLA) and extracted chitosan dispersed biocomposite films were prepared by solution casting method. Significant dispersion of chitosan (extracted at 80 ºC after 10 h) micro‐particles were observed in biocomposite films using FESEM analysis. Due to chitosan interaction with PLA, significant reduction in thermal degradation and activation energy was observed during nonisothermal degradation scan of such films using Flynn‐Wall‐Ozawa and Kissinger‐Akahira‐Sunose models. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43710.     

The influence of processing terms of chitosan membranes made of differently deacetylated chitin on the crystalline structure of membranes

The crystalline structure of chitosan membranes made of a high degree of (90%) and low degree of (60%) deacetylated chitin by various regeneration processes was studied. The results of X-ray and IR spectroscopy investigations testify that the type of crystalline structre, the degree of crystallinity, and the average lateral crystallite size depend basically on the deacetylation degree of the chitin utilized in preparing the membranes. © 1994 John Wiley & Sons, Inc.     

Preparation of highly flexible chitin nanofiber-graft-poly(γ-l-glutamic acid) network film

In the previous study, we successfully prepared a chitin nanofiber film by regeneration from a chitin ion gel with an ionic liquid using methanol. In this study, we performed surface-initiated graft polymerization of γ-benzyl l-glutamate N-carboxyanhydride (BLG-NCA) from amino groups on a partially deacetylated chitin nanofiber (PDA-CNF) film. First, the chitin nanofiber film was immersed in 40 % NaOH aq. at 80 °C for 7 h for partial deacetylation. Then, the PDA-CNF film was immersed in a solution of BLG-NCA in ethyl acetate at 0 °C for 24 h for graft polymerization from amino groups on nanofibers to give a chitin nanofiber-graft-poly(γ-benzyl l-glutamate) (CNF-g-PBLG) film. The analytical results of the film indicated that graft polymerization of BLG-NCA occur on surface of nanofibers. Furthermore, the film was treated with 1.0 mol/L NaOH aq. to convert PBLG on nanofibers into poly(γ-l-glutamic acid sodium salt) (PLGA). Then, condensation of the resulting carboxylates with amino groups at the terminal ends of PLGAs or the remaining amino groups on nanofibers was performed using the condensing agent to produce a CNF-g-PLGA network film. The resulting film showed the good mechanical properties with high flexibility, which has potentials as promising materials for practical applications.     

A new approach for the preparation of chitosan from γ‐irradiation of prawn shell: effects of radiation on the characteristics of chitosan

Chitosan is a biodegradable polymer composed of randomly distributed β‐(1,4)‐linked D ‐glucosamine (deacetylated unit) and N‐acetyl‐D ‐glucosamine (acetylated unit). It is produced commercially by deacetylation of chitin, which is the structural element in the exoskeleton of crustaceans (such as crabs and shrimps) and the cell walls of fungi. In the work reported, we developed a facile technique for the preparation of chitosan by irradiating prawn shell at various intensities from 2 to 50 kGy. It was observed that γ‐irradiation of prawn shell increased the degree of deacetylation (DD) of chitin at a relatively low alkali concentration during the deacetylation process. Among the various irradiation doses applied to prawn shell, a dose of 50 kGy and 4 h heating in 50% NaOH solution yielded 84.56% DD while the chitosan obtained from non‐irradiated prawn shell with the same reaction conditions had only 74.70% DD. In order to evaluate the effect of γ‐irradiation on the various physicochemical, thermomechanical and morphological properties, the chitosan samples were again irradiated (2–100 kGy) with γ‐radiation. Molecular weight, DD, thermal properties with differential scanning calorimetry and thermogravimetric analysis, particle morphology by scanning electron microscopy, water binding capacity (WBC), fat binding capacity (FBC) and antimicrobial activity were determined and the effects of various γ‐radiation doses were assessed. The DD, WBC, FBC and antimicrobial activity of the chitosan were found to improve on irradiation. It was obvious that irradiation caused a decrease of molecular weight from 187 128 to 64 972 g mol^?1 after applying a radiation dose of 100 kGy which occurred due to the chain scission of chitosan molecules at glycosidic linkages. The decrease of molecular weight increased the water solubility of the chitosan, the extent of which was explored for biomedical applications. Copyright © 2012 Society of Chemical Industry     

The effect of reaction time and temperature during heterogenous alkali deacetylation on degree of deacetylation and molecular weight of resulting chitosan

The objective of the study is to elucidate the effect of reaction time and temperature during heterogenous alkali reaction on degree of deacetylation (DD) and molecular weight (MW) of the resulting chitosans, and to establish the reaction conditions to obtain desired DD and MW chitosan products. Chitin was extracted from red shrimp process waste. DDs and MWs were determined by infrared spectroscopy (IR) and static light scattering, respectively. The results are as follow: The DD and MW of chitin obtained were 31.9% and 5637 kDa, respectively. The DD of the resulting chitosan increased along with reaction time and/or reaction temperature. The DDs of the resulting chitosan that were obtained from 140°C were higher than those reacted at 99°C. The highest DD of the resulting chitosans after alkali deacetylation at 99 and 140°C were 92.2 and 95.1%, respectively. The DDs of chitosans increased fast at the beginning of reaction process then slowed over time. The reaction rate and rate constant of the deacetylation reaction decreased with increasing DD of the reactant. The MWs of chitosans decreased along with the deacetylation time. MW of those chitosans reacted at 140°C are smaller than those at 99°C. The rate of chitosan degradation was above 43.6%/h in the initial stage, then decreased to about 20%/h. The degradation rate constants raised substantially in the late stage. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 88: 2917–2923, 2003     

Reactivity characteristics of a new form of chitosan

Summary A new form of chitosan prepared by deacetylating squid -chitin was subjected to N-phthaloylation to evaluate the reactivity as compared with that of the conventional chitosan prepared from shrimp -chitin. The reaction proceeded much more efficiently with squid chitosan than shrimp chitosan to give N-phthaloylchitosan, indicating considerable differences in higher-order structures between the two kinds of chitosans. Squid chitosan thus proved to show enhanced reactivity and be superior to shrimp chitosan as a starting material for controlled regioselective chemical modifications of chitin.     

相转移催化制备壳聚糖

以虾壳为主要原料制得的天然高分子化合物甲壳素和壳聚糖 ,资源丰富 ,应用范围十分广阔。提出了以 3 5 %(质量分数 )氢氧化钠醇水溶液为反应介质 ,并加入相转移催化剂制备壳聚糖的新方法 ,讨论了一些因素对壳聚糖制备过程的影响。     

Physicochemical properties of hydrolyzed and blended chitin

The molecular structures of chitin and chitin hydrolyzed with sodium hydroxide for different time intervals at 160°C were followed using infrared spectroscopy in the range 200–4000 cm^?1. The frequency and intensity of active groups NHCOCH₃, NH₂, OH, and OCH₃ in chitin, chitosan, cellulose, and lignin, respectively, were calculated and correlated with molecular structural changes. The dielectric constant ?′, dielectric loss ?″, and dissipation factor tan δ for the investigated samples were measured in the frequency range 0.1–100 kHz and interpreted in terms of the molecular structure elucidated from the infrared spectroscopic studies. Also, the effect of blending of cellulose and lignin with chitin on their dielectric properties was investigated. It was found that hydrolysis of chitin improved its insulating properties.     

Deacetylation of β‐chitin. I. Influence of the deacetylation conditions

The influences of the deacetylation temperature, deacetylation time, and NaOH concentration on the degree of deacetylation (DD) of deacetylated products prepared from β‐chitin are discussed. The DD values of deacetylated products are related to the ratio of the signal intensities of methyl on acetyl groups and the first anomeric carbon, which are obtained from ¹³C‐NMR spectra. The results show that the DD values of deacetylated product increase as the NaOH concentration, deacetylation time, or deacetylation temperature increases. The thermal properties, chemical structures, and crystalline characteristic of deacetylated products are significantly related to their DD values. Differential scanning calorimetry shows that the peak temperature is slightly increased as the DD values of deacetylated products of β‐chitin increase. Thermogravimetric analysis shows that the thermal degradation onset temperature of deacetylated products decreases as the DD values increase. Fourier transform infrared spectra show that the intensity of a specific absorption peak of ? NH₂ in deacetylated products significantly increases as DD increases. X‐ray diffraction patterns of deacetylated products with DD values of 17.5 and 44.7% have three significant diffraction peaks. However, there are only two diffraction peaks found in products with higher DD values of 76.5 and 94.7%. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2416–2422, 2004     

微波条件下甲壳素脱乙酰反应的条件研究

研究了微波处理条件下,甲壳素脱乙酰反应条件对壳聚糖脱乙酰度的影响。结果表明:微波甲壳素颗粒大小选择为0.18～0.3mm(过60～80目筛)较利于反应。在料液比小于1∶12(质量∶体积)时,壳聚糖脱乙酰度几乎不变,粘度逐渐增大,之后脱乙酰度随料液比的增大而下降。脱乙酰度随碱液浓度的增大而增大。随微波处理时间的延长,脱乙酰度上升、特性粘度下降。微波功率越高,相同时间下,产品的脱乙酰度越高。经正交试验得出:粒度为0.18～0.3mm的甲壳素原料,按料液比1∶12(质量∶体积)加入浓度为50%(质量分数)的NaOH溶液,在微波功率320W下处理21min,所得产品的脱乙酰度可达85.65%,特性粘度为394.07mL/g,灰分为0.05%。