Studies on chitin, 2. Effect of deacetylation on solubility

Abstract

A reproducible method for obtaining water-soluble chitin and a relationship between solubility and degree of deacetylation of chitin were studied. It was found that the regenerated chitin isolated at low temperature from an alkali chitin solution left at 25 "C for 48 to 77 h showed very good solubility in water at 0°C. The degree of deacetylation of an alkaline treated chitin was determined by titration with hydrochloric acid. It increased rapidly to about 75% as the alkaline treatment time increased and began to level off to about 90%, and only the regenerated chitin samples with around 50% of deacetylation were found to be soluble in water. The X-ray diffraction diagrams showed that these were amorphous, although both chitin with lower degree of deacetylation and chitosan had crystallinity. The improved solubility of chitin with about 50% of deacetylation would be attributed to the partial deacetylation which probably brought about the destruction of secondary structure and also the increase of the hydrophilic property on account of the increased number of amino groups. ZUSAM MENFASSUNG : Es wurden eine reproduzierbare Methode zur Darstellung wasserloslichen Chitins und eine Beziehung zwischen Loslichkeit und Entacetylierungsgrad des Chitins untersucht. Dabei wurde gefunden, daB regeneriertes Chitin, das bei niedriger Temperatur aus einer Alkali-Chitin-Losung isoliert wurde, welche 48 bis 77 h bei 25 "C stehen gelassen wurde, eine sehr gute Loslichkeit in Wasser bei 0°C zeigte. Der Entacetylierungsgrad eines mit Alkali behandelten Chitins wurde durch Titration mit Salzsaure bestimmt. Dieser wuchs mit zunehmender Alkali-Behandlungszeit rasch bis ca. 75 % an, um dann langsam bei ca. 90% abzuflachen, wobei nur die Proben des regenerierten Chitins mit etwa 50 % Entacetylierung in Wasser loslich erschienen. Diese waren, wie Rontgenbeugungsdia-*) Part I : cf."). als auch Chitosan Kristallinitat aufwiesen. Die verbesserte Loslichkeit des Chitins mit ca. 50% Entacetylierung ist wohl auf die partielle Entacetylierung zuriickzufiihren, durch die wahrscheinlich eine Zerstorung der Sekundarstruktur bewirkt wurde, und auf die Zunahme des hydrophilen Charakters durch die erhohte Zahl an Aminogruppen.

Action Pattern ofBacillussp. No. 7-M Chitosanase on PartiallyN-Acetylated Chitosan

“…Chitosan samples with different degrees of deacetylation were prepared by homogeneous or heterogeneous alkaline hydrolysis of chitin. The homogeneous hydrolysis was done by a modification of the method of Sannan et al 8 ) Chitin was suspended in 42% NaOH for 1 week at room temperature, and crushed ice was added to the suspension to reduce the concentration ofNaOH to 5%. The solution was kept at 50°C for 24 hr and 168 hr.…”

Characterization of Some Fungal Chitosans

“…The degrees of N-acetylation of the samples insoluble in 0.5% acetic acid, were measured by the conductometric titration method. 9 ) Molecular weigth measurement ofchitosans. Molecular weights of various chitosans were measured by gel permeation chromatography (Tosoh Co., Ltd.), in which 0.025% chitosan samples were eluted with a solvent containing 0.5 M acetic acid and 0.5 M sodium acetate, and polyethylene oxide as the standard sample.…”

“…9 ) The results are shown in Tables I and II. Fungal chitosans showed various degrees of Nacetylation between 5 and 59% (Table I).…”

Compilation of analytical methods to characterize and determine chitosan, and main applications of the polymer in food active packaging Recopilación de métodos analíticos para la caracterización y determinación del quitosano y las principales aplicaciones del polímero en los envases activos alimentarios

“…Different types of titration have been used with chitosan: isothermal titration calorimetry (ITC) (Kim, 2004), turbidimetric titration (Rosca, Popa, Lisa, & Chitanu, 2005), acid-base titration (Arcidiacono & Kaplan, 1992;Sannan, Kurita, & Iwakura, 1976 With ITC, thermodynamic bindings can be determined through measurements of the molecular interactions' energy at constant temperatures. ITC provides the number of binding sites of chitosan, its binding constant, and the enthalpy of binding (Kim, 2004).…”