P. F. Vidal

A rapid method for the determination of the degree of N-acetylation of chitin-chitosan samples by acid hydrolysis and HPLC

Abstract A simple and rapid method for the quantitative determination of N -acetyl groups in chitin-chitosan samples consists of an acid hydrolysis conducted at high temperature with a mixture of sulfuric and oxalic acids. The acetic acid formed is determined by spectrophotometry at 210 nm after separation from the reaction mixture by HPLC. The method is valid for the entire range of degrees of acetylation and the results compare fairly to those of other techniques.

Purification and characterization of a chitosanase from Streptomyces N174

A highly efficient chitosanase producer, the actinomycete N174, identified by chemotaxonomic methods as belonging to the genus Streptomyces was isolated from soil. Chitosanase production by N174 was inducible by chitosan or d-glucosamine. In culture filtrates the chitosanase accounted for 50–60% of total extracellular proteins. The chitosanase was purified by polyacrylic acid precipitation, CM-Sepharose and gel permeation chromatography. The maximum velocity of chitosan degradation was obtained at 65° C when the pH was maintained at 5.5. The enzyme degraded chitosans with a range of acetylation degrees from 1 to 60% but not chitin or CM-cellulose. The enzyme showed an endo-splitting type of activity and the end-product of chitosan degradation contained a mixture of dimers and trimers of d-glucosamine.

Polyionic Hydrogels Obtained by Complexation between Xanthan and Chitosan: Their Properties as Supports for Enzyme Immobilization

A method for the preparation of hydrogels from the complexation of chitosan and xanthan is reported. Stable hydrogels capable of retaining be tween 65 and 95% weight water were prepared. The water retention and prop erties of the hydrogels were studied as a function of the degree of acetylation of chitosan and the ratio chitosan/xanthan used in the preparation of the gel. Spectroscopic FTIR was used to confirm complexation between the amine (chi tosan) and carboxylic (xanthan) groups. Electron micrographs (SEM and TEM) show the formation of a fibrillar structure with characteristic pore sizes be tween 100 and 1000 nm and fibril diameters between 50 and 100 nm. The diffu sion coefficient of 4-O-methyl-d-glucurono-D-xylan Remazol Brilliant Blue R (RBB-xylan) in the complex chitosan-xanthan was 2.02 × 10-12 m 2s-1 at 30°C. The chitosan-xanthan complex was used to immobilize two enzymes (endo-1,4- β-xylanase and protease) either as single enzymes or as a binary system. Immo bilization varied between 85 and 98%. The immobilized xylanase activity was significantly greater with respect to the free enzyme while the binary enzyme system promoted protease activity.

Characterization of depolymerized cellulosic residues. Part 2: Residues derived from ethylene glycol solvolysis of cellulose.

SummaryCellulose can be depolymerized by thermo-mechanical treatment at high temperature using ethylene glycol as solvent. A fraction of the cellulose is solubilized and the solid residual fraction consists of highly ordered cellulose with very low degree of polymerization and exhibits very high accessibility to enzymatic attack. Chemical characterization by thermal and spectroscopic techniques has shown that no chemical degradation occurs during depolymerization even if structural reorganization has been observed. Comparison with cellulose depolymerization byaqueous acid hydrolysis processes has shown the superior characteristics of the solvolytic process. The latter yields depolymerized cellulosic residues with increased accessibility to cellulases hydrolysis whereas the acid hydrolysis process even at very mild conditions results in functional modifications of the depolymerized cellulosic residue.

Polyionic hydrogels as support for immobilization of lipase

Polyionic hydrogels have been prepared by complexation of chitosan and xanthan. These hydrogels have been used to immobilize lipase from porcine pancreas (E.C. 3.1.1.3). Immobilization efficiency varied between 90 and 99% of initial activity. Immobilized lipase retained its activity towards hydrolysis of olive oil in water as an emulsion and of olive oil in isooctane.

Alkaline Oxidation of Sugar : Thermochemical Conversion of Xylose from Hemicellulose into Lactic Acid

Hemicelluloses are the first extracted fraction in numerous fractionation processes of lignocellulosic basic materials. Acid hydrolysis of hemicelluloses give a mixture of carbohydrates in which xylose is often in a majority. Transforming these carbohydrates into lactic acid is an interesting objective due to its numerous applications.

The Hydrolysis of Peat at Short Residence Time Using Tubular Reactors: Characterization of the Hydrolyzate

Peat has been treated as a 10–12% solids water suspension in a continuous process development unit at a flow rate of 1 liter/minute. The unit is equipped with a shearing device in order to destructurate the material. The temperature has been varied between 175 and 225°C, the residence time being of 2 minutes. Two operating regimes have been considered: autohydrolysis and acid hydrolysis.