Preparation and Characterization of Chitosan Obtained from Shells of Shrimp ( Litopenaeus vannamei Boone)

Abstract

The main source of commercial chitosan is the extensive deacetylation of its parent polymer chitin. It is present in green algae, the cell walls or fungi and in the exoskeleton of crustaceans. A novel procedure for preparing chitosan from shrimp shells was developed. The procedure involves two 10-minutes bleaching steps with ethanol after the usual demineralization and deproteinization processes. Before deacetylation, chitin was immersed in 12.5 M NaOH, cooled down and kept frozen for 24 h. The obtained chitosan was characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), UV, X-ray diffraction (XRD) and viscosimetry. Samples of white chitosan with acetylation degrees below $9\%$ were obtained, as determined by FTIR and UV-first derivative spectroscopy. The change in the morphology of samples was followed by SEM. The ash content of chitosan samples were all below $0.063\%$ . Chitosan was soluble in $1\%$ acetic acid with insoluble contents of $0.62\%$ or less. XRD patterns exhibited the characteristic peaks of chitosan centered at 10 and 20 degrees in $2\theta$ . The molecular weight of chitosan was between 2.3 and 2.8 $\times {10}^5$ g/mol. It is concluded that the procedure developed in the present work allowed obtaining chitosans with physical and chemical properties suitable for pharmaceutical applications.