Improved method for production of chitin and chitosan from shrimp shells.

In this study, pretreatment procedures have been investigated preceding the standard production of chitin and chitosan. These steps can be used in industrial processes to preserve raw shrimp shells as long as the amount of material is not enough for one production batch. After these treatments, shrimp shells are clean and are facile for further demineralization, deproteinization and deacetylation processes.

Preparation of water soluble hydrochloric chitosan from low molecular weight chitosan in the solid state.

In this study, low molecular weight chitosan salt (LMWC-HCl) highly soluble in water was prepared from low molecular weight chitosan (LMWC) in the solid state exposed to hydrogen chloride gas as a reagent. The effects of chitosan particle size, exposure conditions, reaction temperature and reaction time were investigated on the solubility and the molecular weight of obtained products. The formation of the chloride salt was observed after 3 h in a range of temperatures from 4 to 50 °C.

Selection of a practical assay for the determination of the entire range of acetyl content in chitin and chitosan: UV spectrophotometry with phosphoric acid as solvent.

The rapidly expanding use of chitomaterials in biomedical applications demands accurate and precise analytical methods to determine physico-chemical characteristics, especially the acetyl content of the sample. The analytical methods available for the determination of the acetyl content of the biomaterials are quite different in efficiency, accuracy and precision. Out of 22 analytical methods reviewed, XRD, DSC, FTIR (KBr pellet), solid state (13)C CP/MAS NMR, and acid hydrolysis-HPLC and the spectrophotometry assay using phosphoric acid as solvent (PUV) were selected in this study.

Decomposition of myceliar matrix and extraction of chitosan from Gongronella butleri USDB 0201 and Absidia coerulea ATCC 14076.

Free chitosan, 2 g/100g mycelia from Gongronella butleri and 6.5 g/100g mycelia from Absidia coerulea were isolated by 1M NaOH at 45 degrees C for 13 h and 0.35 M acetic acid at 95 degrees C for 5 h.

Ionotropic cross-linked chitosan microspheres for controlled release of ampicillin.

The solubility of non cross-linked chitosan in weak acid solutions restricts its utility in microspheres for drug delivery. The primary aim of this study was to produce pentasodium tripolyphosphate cross-linked chitosan microspheres with higher acid resistance for controlled release of ampicillin. The microspheres were prepared by two different microencapsulation procedures (by emulsification and by spray-drying) and characterized by their particle size, surface morphology, stability, drug entrapment efficiency and drug release.

Evaluation of an improved acid hydrolysis-HPLC assay for the acetyl content in chitin and chitosan.

Functional properties of the amino polysaccharides, chitin and chitosan, vary significantly with their acetyl content. The acid hydrolysis-HPLC method offers good accuracy and precision to assay the acetyl content regardless of the solubility of the sample. In this research, the hydrolysis parameters were changed, and the analytical method was counterchecked with other methods.

Functional characteristics of shrimp chitosan and its membranes as affected by the degree of deacetylation.

The functional properties of three shrimp chitosan preparations with different degrees of deacetylation (75%, 87% and 96% DD) but with a constant molecular weight (about 810 kDa) were investigated. Chitosan with 75% DD had a 1.5 times higher water absorption, probably due to its 20% lower level of crystallinity.

Peripheral enzymatic deacetylation of chitin and reprecipitated chitin particles.

The enzymatic deacetylation of various chitin preparations was investigated using the fungal chitin deacetylase (CDA) isolated from Rhizopus oryzae growth medium. Specific extracellular enzyme activity after solid state fermentation was 10 times higher than that after submerged fermentation. Natural crystalline chitin is a very poor substrate for the enzyme, but showed a five-time better deacetylation after dissolution and reprecipitation.

Chitosan-alginate multilayer beads for controlled release of ampicillin.

The aim of this study is to develop multilayer beads with improved properties for controlled delivery of the antibiotic ampicillin. Ionotropic gelation was applied to prepare single and multilayer beads using various combinations of chitosan and Ca(2+) as cationic components and alginate and polyphosphate as anions. Beads prepared with higher concentrations of chitosan entrapped more ampicillin.

Expression of chitin deacetylase from Colletotrichum lindemuthianum in Pichia pastoris: purification and characterization.

The chitin deacetylase gene from Colletotrichum lindemuthianum UPS9 was isolated and cloned in Pichia pastoris as a tagged protein with six added terminal histidine residues. The expressed enzyme was recovered from the culture supernatant and further characterized. A single-step purification based on specific binding of the histidine residues was achieved.

Transdermal delivery controlled by a chitosan membrane.

The release of a drug from a transdermal delivery system with a rate controlling chitosan membrane was analyzed in vitro and in vivo. Lidocaine hydrochloride, a local anesthetic, was used as the model drug. The in vitro permeability of various chitosan membranes for the drug was investigated using a Franz diffusion cell.

Chitosan membrane as a wound-healing dressing: characterization and clinical application.

Chitosan prepared from natural biopolymer chitin and cast into membranes has been tested as wound dressing at the skin-graft donor site in patients. Bactigras, a commonly used impregnated tulle gras bandage, served as a control. Chitosan membrane, prepared with a 75% degree of deacetylation and a thickness of 10 microm, was used in nonmesh or mesh form.

Genetically modified soybeans: false-positive detection in fermented natural soybean (tempe).

Tempe was prepared using mixtures of natural soybean and genetically modified Roundup Ready (RUR) soybean fermented with natural Rhizopus sp. The amount of RUR soybean was quantified using an ELISA plate test. The RUR signal decreased during fermentation.

Characterization of decrystallized chitosan and its application in biosorption of textile dyes.

Decrystallized chitosan was produced from shrimp shells with a low degree of crystallinity (10%) and a high anionic dye binding capacity. Raw, mixed dye wastewater from a textile factory was efficiently decolorized using decrystallized chitosan that was more efficient than using normal chitosan and activated carbon. Decolorization reached 90% within 10 min and could be carried out from pH 4.

Quantification and characterization of insoluble chitinous materials in viscous chitosan solutions.

Insoluble chitinous materials in highly viscous chitosan solutions can be quantified using the viscosity-lowering action of transglucosidase (EC 2.4.1.

Chitosan-alginate multilayer beads for gastric passage and controlled intestinal release of protein.

Chitosan-alginate beads loaded with a model protein, bovine serum albumin (BSA) were investigated to explore the temporary protection of protein against acidic and enzymatic degradation during gastric passage. Optimum conditions were established for preparation of homogenous, spherical, and smooth chitosan-alginate beads loaded with BSA. Multilayer beads were prepared by additional treatment with either chitosan or alginate or both.

Genetic analysis of the interface between Cdc42p and the CRIB domain of Ste20p in Saccharomyces cerevisiae.

Mutagenesis was used to probe the interface between the small GTPase Cdc42p and the CRIB domain motif of Ste20p. Members of a cluster of hydrophobic residues of Cdc42p were changed to alanine and/or arginine. The interaction of the wild-type and mutant proteins was measured using the two-hybrid assay; many, but not all, changes reduced interaction between Cdc42p and the target CRIB domain.