All reagents were of either analytical grade or the highest purity grade available. Chitin was obtained from shrimp (Pleoticus mu¨ lleri) wastes at the Laboratoriode Investig aciones Ba´ sicas y Aplicadas en Quitina (LIBAQ). Raw material was homogenized and triturated in an industrial triturator (Westinghouse model DASO6). The product was rinsed with
water at room temperature in order to remove organic materials. The cleaned residue was treated with 9% (w/w) NaOH at 65 1C for 90 min to remove proteins, then demineralized by treatment with 10% (v/v) HCl at 20 1C for 15 min. Finally the obtained chitin was washed with water at room temperature, and then air-dried. Chitosan was obtained from chitin
by heterogeneous de acetylation at 136 1C with 50% (w/w) NaOH for 1 h. The characteristics of chitosan used in this study were: de acetylation degree: 95, moisture: 6.0%, ash content: 0.55%.