Abstract
•Chitin and chitosan were isolated from shrimp shell by mechanical and chemical treatment.•Obtained biopolymers were characterized by analytical methods (elemental analysis, FTIR, etc.).•The antibacterial activity of the chitin and chitosan against Gram negative bacteria Escherichia coli was evaluated and compared with commercial biopolymers.
Chitin and chitosan were obtained by chemical treatments of shrimp shells. Different particle sizes (50–1000μm) of the raw material were used to study their effect on size distribution, demineralization, deproteinization and deacetylation of chitin and chitosan isolation process. The particle size in the range of 800–1000μm was selected to isolate chitin, which was achieved by measuring nitrogen, protein, ash, and yield %. Hydrochloric acid (5%, v/v) was optimized in demineralization step to remove the minerals from the starting material. Aqueous solution of sodium hydroxide (5%, w/v) at 90°C for (20h) was used in deproteinization step to remove the protein. Pure chitin was consequently impregnated into high concentration of sodium hydroxide (50%) for 3.5h at 90°C to remove the acetyl groups in order to form high pure chitosan. The degree of deacetylation (DDA) of chitosan was controlled and evaluated by different analytical tools. The chemical structure of chitin and chitosan was confirmed by elemental analysis, ATR-FTIR, H/C NMR, XRD, SEM, UV–Vis spectroscopy, TGA, and acid–base titration. The isolated chitin and chitosan from shrimp shell showed excellent antibacterial activity against Gram (−ve) bacteria (Escherichia coli) comparing with commercial biopolymers.