Molecular Insights into the Biosynthesis of Insect Cuticles.

Controlling branching structure formation of the salivary gland by the degree of chitosan deacetylation

Nowadays chitosan becomes more and more important as a drug carrier. In this study the influence of different degrees of de-acetylation of chitosan on the cytotoxicity were investigated. Materials and Methods: Chitosan (87%, 70% and 40% de-acetylated) was analysed for their cytotoxic effect on mouse Balb/c 3T3 fibroblast cells as well as two different human tooth pulp fibroblast cell-lines. The cell survival rate was determined over a 24 hour period according to the standard MTT assay. Results: The Univariate ANOVA test showed significant differences in the cell survival rates (p<0.01) amongst 87% and 70% and 40% de-acetylated chitosan products for the 3T3 as well as the two pulp fibroblast cell-lines. Significant differences were also found between both tooth cell-lines and the 3T3 cell-line at all 3 different de- acetylated chitosan levels. The 3T3 cell line was mostly affected at 40% de-acetylation. The difference between both human cell-lines was not significant. Conclusion: The lower the degree of chitosan de-acetylation the less the cell survival rate while an 87% de- acetylation degree improved the cell survival rate. Different cell lines react differently towards different degrees of de-acetylation. The relative survival rates of different cell lines changed at different degrees of de-acetylation.

Partial removal of acetyl groups in konjac glucomannan significantly improved the rheological properties and texture of konjac glucomannan and κ-carrageenan blends

An investigation on the short-term biodegradability of chitosan with various molecular weights and degrees of deacetylation

The palm stearin and palm kernel olein (PSPKOo) blend (at 31%) was incorporated into chitosan of different degree of deacetylation (DD) (85 and 95%) and molecular weight (MW) (100,000 and 300,000 Da) to form films, and the films were evaluated in terms of particle size, diameter and stability of emulsion, as well as thickness and tensile strength. The chitosan with 85% DD (MW 300,000 Da) and 31% PSPKOo blend resulted in the strongest film, while this chitosan varied with 15.5 and 31% of PSPKOo blends compared to physical properties of film. Emulsion blend containing 85% DD (MW 300,000 Da) and 31% PSPKOo blend of chitosan gave the biggest particle size, highest viscosity and the most stable emulsion, resulting in the thickest film with the highest tensile strength (TS) and elastic modulus (EM). The film was applied on cherry tomato and stored at 20C for 9 days. The chitosan film with 85% DD (MW 300,000 Da) and 31% PSPKOo blend was the most effective in reducing weight loss and maintaining firmness and redness of cherry tomato compared to the other two films. Hence, palm stearin (PS) showed potential to be used as a moisture barrier in fruit coating. Practical Applications This paper presents an alternative edible coating and film of chitosan with the incorporation of palm stearin and palm kernel olein blends. The palm stearin and palm kernel olein blend has limited applications due to its properties meanwhile available in a low price. This preservation method makes it possible to prolong the postharvest life of fruits and useful for fruit producers by reducing the quality changes through a better understanding of the coating/film applications.

The polymeric structure characteristics of β-chitosan from jumbo squid (Dosidicus gigas) pens and α-chitosan from shrimp shells during depolymerization by cellulase hydrolysis at different degrees of deacetylation (DDA) (60, 75, and 90%) were investigated by using Fourier transform infrared spectroscopy and X-ray diffraction. Antibacterial activity of β-chitosan against Escherichia coli and Listeria innocua was compared with that of α-chitosan at similar Mw and degrees of deacetylation (DDA) by studying inhibition ratio and minimal inhibition concentration (MIC) and was coordinated with the structural characteristics of the two forms of chitosan. β-Chitosan was more reactive to cellulase hydrolysis than α-chitosan due to its relatively lower crystallinity (CI) and loose crystal property, and the 75% DDA chitosan was more susceptible to cellulase than the 90% DDA ones with the 75% DDA of β-chitosan mostly reactive. Both forms of chitosan showed more inhibition against E. coli than against L. innocua, and no difference against L. innocua between the two forms of chitosan was observed. However, the two forms of chitosan exhibited different levels of antibacterial activity against E. coli, in which 75% DDA/31 kDa β-chitosan demonstrated significantly higher inhibition (lower MIC) than that of 75% DDA/31 kDa α-chitosan, whereas 90% DDA/74-76 kDa α-chitosan had a higher inhibition ratio than that of 90% DDA/74-76 kDa of β-chitosan. This result may be explained by the impact of the different structural properties between α- and β-chitosan on chitosan conformations in the solution. This study provided new information about the biological activities of β-chitosan, a bioactive compound with unique functionalities and great potential for food and other applications.

Effect of konjac glucomannan with different degrees of deacetylation on the gel behavior of transglutaminase induced soybean protein isolate emulsion gels

A series of chitosan membranes and their N-acetylated counterparts were prepared and their differences in acidic solution stability and thermal and mechanical properties were studied. The differences were attributed to differences in crystallinity of the membrane as the result of preparation conditions and N-acetylation. The results show that after N-acetylation, the acidic solution stability of N-acetylated membranes increased and the tensile strengths and the enthalpies of those membranes prepared from lower DD chitosans became higher and those from higher DD ones became lower. However, the swelling index of those modified membranes prepared from lower DD chitosans decreased and that from higher DD chitosans increased. Original membranes were prepared by using chitosans with different degrees of deacetylation (DD) and solution pHs to manipulate different chain flexibilities. © 1996 John Wiley & Sons, Inc.

In order to study the relationship between the degree of deacetylation of chitin whiskers (CHWs) and their enzymatic degradation properties, in this paper, CHWs were first deacetylated to different degrees by alkali treatment, and the CHWs with the degrees of deacetylation of 17.84, 67.76, and 82.54% was obtained, respectively. Moreover, the partially deacetylated CHWs still maintained good crystallinity and nanoneedle-like morphology. Next, the in vitro degradation behavior of CHWs with different degrees of deacetylation was further studied under the single or synergistic action of lysozyme and lipase (37 °C, pH = 7.4). The results showed that the morphology change of CHWs was more obvious as the degree of deacetylation increased. The mass loss, the crystallinity index at the (110) crystal plane, and the concentration of reducing sugar of the CHWs also increased with the degree of deacetylation. Moreover, the synergistic effect of the two enzymes was more conducive to the degradation process of CHWs than single lysozyme or lipase. The difference in the rate of enzymatic degradation provides an idea for the regulation of the degradation rate of the CHWs.

Confirmation and measurement of hydrophobic interaction in sol-gel system of konjac glucomannan with different degree of deacetylation

Molecular dynamics (MD) simulations were performed to calculate the interaction between chitosan at different degrees of deacetylation (DD) and carbon nanotubes (CNTs) functionalized with either amine (−NH2) or carboxylic (−COOH) groups. The objective was to elucidate the effect of the CNT functionalization type and the different DD of chitosan on the mechanical properties of the nanocomposite. For a certain DD, where the glucosamine and acetyl-glucosamine units are uniformly distributed along the chitosan chain, MD simulations showed that this molecule depicts a large contacting superficial area that allows the interaction with the functionalized CNT. It was also found that the attractive interaction between a 50% DD chitosan and the −NH2 functionalized CNT (CNT–NH2) was the strongest among the different deacetylated cases under study. For the 50% DD case, a wrapping effect of the CS chain around the CNT–NH2 structure was displayed which was attributed to hydrogen bonds formation between the amine groups in the CNT and the −OH and −NH2 groups in the chitosan molecule. Composite films of chitosan, reinforced with multiwall carbon nanotubes (MWCNT) functionalized with either −NH2 (MWCNT–NH2) or −COOH (MWCNT–COOH), were prepared to measure their Young’s module. The experiments showed that the films reinforced with MWCNT–NH2 exhibited larger Young’s modules than those functionalized with −COOH groups. The above was due, likely, to the strong interaction between the amino functionalized CNTs and the polymeric matrix. The simulation results were in agreement with the experimental data.

Partially deacetylated chitins with different degrees of deacetylation (DD) were prepared by alkaline treatment under homogeneous conditions, and the effect of DD on their solubility was discussed in terms of crystal structure and mode of hydrogen bonding. With an increase in the treatment time, the DD of chitin increased proportionally. The chitin became soluble in dilute acetic acid at the DD of ca. 28% or over and soluble in water at the DD of ca. 49%. The solubility of the partially deacetylated chitins had a close relationship with their crystal structure, crystallinity, and crystal imperfection as well as the glucosamine content. The wide-angle X-ray diffractometry (WAXD) revealed that the chitin with ca. 28% DD retained the crystal structure of alpha-chitin with significantly reduced crystallinity and perfection of the crystallites. The water-soluble chitin of ca. 49% DD had a new crystal structure similar to that of beta-chitin rather than either alpha-chitin or chitosan, suggesting that the homogeneous deacetylation transformed the crystal structure of chitin from the alpha to the beta form. Some hydrogen bonds existing in raw alpha-chitin were found to be missing at a DD of ca. 49%.

The present study was conducted to evaluate whether the deacetylation degree of chitosan (low: 70% vs. high: 90%) and its dietary level (0, 200, 400, 800, 1600 mg/kg diet) would affect laying performance, faeces viscosity, egg quality, egg and serum biochemistry of layers. For the experimental feeding period of 8 weeks, 140 four weeks old Hisex Brown layers were divided into 10 treatment groups, comprising 14 birds each. The birds were housed in individual cages in a complete randomised design. Performance was assessed by recording feed intake, egg weight, daily egg production, egg quality and egg biochemistry. Serum biochemistry parameters were determined at the beginning and end of the experiment and faeces viscosity at the end of the experiment. Feed conversion ratio and faeces viscosity were deteriorated by increased level of chitosan. Lightness of egg yolk was significantly increased in animals receiving high-degree deacetylated chitosan compared to low-degree deacetylated chitosan. Yellowness of egg yolk was affected by interaction of deacetylation degree and level of chitosan. Yolk cholesterol concentration was lower in groups receiving high deacetylated chitosan by increasing chitosan level, while laying hens fed low deacetylated chitosan had a higher level of yolk cholesterol. A significant interaction between degree of deacetylation and chitosan level was determined for serum glucose and calcium concentration. Serum total antioxidant content increased with higher levels of dietary chitosan. In conclusion, dietary level or different degrees of deacetylated chitosan may reduce yolk cholesterol and improve serum antioxidant status. However, feed conversion ratio and faeces viscosity were impaired by increasing levels of chitosan supplementation, and lightness of yolk was increased by supplementation of chitosan with a high degree of deacetylation.

Reactive oxygen species scavenging activity of aminoderivatized chitosan with different degree of deacetylation

The degree of deacetylation is the proportion of glucosamine monomer residues in chitin. It affects many properties of chitosan. The objectives of this research were to study the deacetylation of chitin by alkaline and to investigate chitosan film properties with different degrees of deacetylation. Chitin was deacetylated by boiling (95°C) in concentrated sodium hydroxide (50%) solution for 120-300 minutes. The degree of deacetylation of chitosan was determined by potentiometric titration method. Chitin possessed a degree of deacetylation of 7.74%. The alkaline deacetylation produced chitosan with a degree of deacetyl- ation of 15.24-70.19%. We found a linear relationship between the degree of deacetylation and deacetylation time (degree of deacetylation = 2.476 + 0.230t, R 2 = 0.915). The deacetylation time had no effect on the yield and whiteness of the obtained chitosans. Film was formed from the obtained chitosan at each deacetylation time and their properties investigated. Increasing the deacetylation time increased the tensile strength, elongation and water vapor transmission rate of the films. In contrast, redness (a*) and yellowness (b*) of the films decreased.