Produção de Quitosana a partir dos Caranguejos Dilocarcinus pagei Stimpson, 1861, Capturados no Município de Itacoatiara (AM)

Abstract

The exoskeleton of crustaceous is one of the main sources of chitin, a biopolymer precursor of chitosan. This work aimed the extraction of chitin from the residues of the Dilocarcinus pagei crab collected in the city of Itacoatiara (AM), and eventually converted to chitosan and also the analysis of the physicochemical properties of the obtained materials. The demineralization step used acid solutions of different concentrations and under different reaction times, in which the condition using acid solution of 0.50 mol L-1 and reaction time of 30 minutes exhibited greater mass loss. Removal of the organic content occurred through the contact of the demineralised remnant with 1.0 mol L-1 NaOH solutions at 70 ° C for different time lengths, where a larger mass loss was observed for the 24-hour period. Chitin was obtained by exposing the deproteinized material to a 0.14 mol L-1 NaClO solution for 8 hours. From the analysis of the final yield of each stage, it was found that the residues of the Amazonian crab is constituted by 78.4 5% CaCO3 and 21.55 % organic matter. Of the organic fraction, 51.93 % (10.99 % of the initial mass of the residues) consists of proteins and lipids, whereas 48.07 % (10.56 % of the initial mass of the residues) consists of an association of chitin and pigments. From this association, 23.95 % (2.53 % of the initial mass of the residues) is formed by pigments and 76.05 % (8.03% of the initial mass of the residues) is formed by chitin. The content of chitin found is similar to that found in the literature for other species of crab. According to X-ray diffraction and thermogravimetric analysis, it was verified that the chitin obtained has diffraction patterns characteristic of the α-chitin crystallographic phase and the obtained chitosan has semi-crystalline structure. The thermal decomposition profile is characteristic of biopolymers, with the existence of non oxidative and oxidative events of mass loss. It was found through Infrared spectroscopy that the degree of deacetylation of the obtained chitosan samples after chitin treatment with 10.0 mol L-1 NaOH solution at 105 º for 60, 90 e 120 minute were between 68.45 % and 81.92 %.