Hitoshi Sashiwa

Evaluation of different absorbance ratios from infrared spectroscopy for analyzing the degree of deacetylation in chitin

Various acetylated chitosan derivatives and mixtures of chitin and chitosan, covering the range of the degree of deacetylation (DDA) from 0-100% were analyzed by 1H-NMR spectroscopy and infrared spectroscopy. The use of the 1070 cm-1 or 1030 cm-1 absorption band as an internal standard in the determination of DDA from the absorbance of the amide I bands at 1655 cm-1 and 1630 cm-1 or the amide II band at 1560 cm-1 was studied. There is a good correlation between the results from IR spectroscopy and those from 1H-NMR spectroscopy.

Preparation and characterization of water-soluble chitin and chitosan derivatives

Chitosan was modified with poly(ethylene glycol)-aldehyde (PEG-aldehyde) of various molecular weights under the various molar ratios of PEG-aldehyde to chitosan. Then the prepared chitosan-PEG hybrid was converted to chitin-PEG hybrid by the acetylation with acetic anhydride. The solubility of various derivatives was investigated in three buffers of various pH. Some of these derivatives were soluble in 0.01 M phosphate buffer saline (PBS, pH = 7.2). The solubility in PBS was dependent on the degree of PEG substitution, the degree of acetylation, the molecular weight of PEG, and the weight ratio of PEG in chitin/chitosan-PEG hybrid.

Chemical modification of chitin and chitosan 2 : preparation and water soluble property of N-acylated or N-alkylated partially deacetylated chitins

N-Acylated partially deacetylated chitin (DAC-88) derivatives were prepared via ring-opening reactions with various cyclic acid anhydrides in aqueous MeOH system. N-Alkylation of DAC-88 were also performed in aqueous MeOH with various aldehydes, monosaccharides, and disaccharides. The water solubility of N-acylated and N-alkylated chitosan derivatives at various pHs were studied.

Enzymatic degradation of chitins and partially deacetylated chitins.

The enzymatic (lysozyme, chitinase etc.) digestibility of chitins obtained from squid pen and shrimp shell, and of partially deacetylated chitins (DA-chitins) was investigated. The digestibility of various chitins by the chitinase from Bacillus sp. PI-7S was much higher than that by lysozyme, and beta-chitin was digested more smoothly than alpha-chitin. DA-chitin deacetylated under homogeneous conditions (DAC) was hydrolysed by lysozyme more rapidly than that deacetylated under heterogeneous conditions (DAC). DACs from shrimp shell and squid pen showed the same degree of digestibility by lysozyme in spite of a difference in the crystal structure of the original chitins. The crystal structure of chitin and the degree of N-acetyl group aggregation among DA-chitin molecules affect the enzymatic digestibility of chitin and DA-chitin, respectively.

Lysozyme susceptibility of partially deacetylated chitin.

Lysozyme susceptibility of partially deacetylated chitins (DACs) was investigated by viscometric and gel permeation chromatographic procedures. The highest lysozyme susceptibility was shown by the DAC of around 70% deacetylation which have already been reported to have the highest immunoadjuvant activity through mouse peritoneal macrophage activation.

Production of N-acetyl-D-glucosamine from α-chitin by crude enzymes from Aeromonas hydrophila H-2330

The selective and efficient production of N-acetyl-D-glucosamine (GlcNAc) was achieved from flake type of alpha-chitin by using crude enzymes derived from Aeromonas hydrophila H-2330.

Enzymatic production of N-acetyl-D-glucosamine from chitin. Degradation study of N-acetylchitooligosaccharide and the effect of mixing of crude enzymes

N-Acetyl-D-glucosamine (GlcNAc) was produced from chitin by use of crude enzyme preparations. The efficient production of GlcNAc by cellulases derived from Trichoderma viride (T) and Acremonium cellulolyticus (A) was observed by HPLC analysis compared to lipase, hemicellulase, and pectinase. b-Chitin showed higher degradability than a-chitin when using cellulase T. The optimum pH of cellulase T was 4.0 on the hydrolysis of b-chitin. The yield of GlcNAc was enhanced by mixing of cellulase T and A. q 2003 Elsevier Science Ltd. All rights reserved.

Chemical modification of chitosan. Part 15: Synthesis of novel chitosan derivatives by substitution of hydrophilic amine using N-carboxyethylchitosan ethyl ester as an intermediate

The Michael type reaction of chitosan with ethyl acrylate has been investigated. Although this reaction was quite slow in the case of chitosan, the reiteration of the reaction was an effective means for increasing the degree of substitution (DS) of ethyl ester. The N-carboxyethylchitosan ethyl ester as an intermediate was successfully substituted with various hydrophilic amines, although the simultaneous hydrolysis of the ester to carboxylic acid also occurred. Water-soluble chitosan derivatives were obtained by substitution with hydroxyalkylamines and diamines.

N-acetyl group distribution in partially deacetylated chitins prepared under homogeneous conditions

The distribution of N-acetyl group in partially deacetylated chitin (DA-chitin) was investigated by nitrous acid deamination. Most deamination products of various DA-chitins (over 50% of deacetylation), prepared under homogeneous conditions, were oligomers of less than six units. These results would suggest a random distribution of N-acetyl groups in the DA-chitin molecule.

Influence of physico-chemical properties of chitin and chitosan on complement activation

Abstract To recognize the complement activation by chitin and chitosan, various physico-chemical aspects were studied. Complement activation was determined by change of plasma C3 concentration using single radial immunodiffusion method. Results were as follows: in samples with homogeneous acetylation (oDAC), C3 concentration was decreased with the increase in the degree of acetylation of oDAC. In oDACs 50 and 42 (water soluble materials), however, C3 was not decreased. In samples with heterogeneous acetylation or deacetylation samples (eDAC), all samples showed C3 activation even in eDAC 53 (solid material) and have almost same activity on complement activation. C3 activation was not seen in low molecular weight materials including d -glucosamine. The important factors inducing complement activation by chitosan-based mucopolysaccharide should be solids. The samples with heterogeneous acetylation (eDACs) had a stable ability on complement activation than with homogeneous acetylation (oDACs).