The impact of re-ordering the conventional chemical steps on the production and characterization of natural chitosan from biowaste of Black Tiger Shrimp, Penaeus monodon

Abstract

Chitosan is a biopolymer compound which is made up of β-1,4 glycosidic bonds. Due to its peculiar nature, chitosan has found applications in science and engineering, food processing, medicine, agriculture and wastewater treatment. Isolation of chitin and chitosan from dry powder shell of Penaeus monodon was achieved through chemical treatment with acid and alkali. The conventional sequence of chemical isolation of chitosan follows the order of demineralization (DM), deproteinization (DP), decoloration (DC) and deacetylation (DA). This was altered into four different sequential protocols: SQ1(sequence 1), SQ2 (sequence 2), SQ3 (sequence 3) and SQ4 (sequence 4) to study its effect on the physicochemical properties of chitosan. 1 M HCl and 2 M NaOH was applied at 1:15 m/v ratio for 3 h to achieve demineralization and deproteinization, respectively. Furthermore, for all sequences, deacetylation of chitin to produce chitosan was achieved by application of 50% NaOH at 100 °C for 3 h. In the present study, the chemical structures of chitosan were confirmed through FTIR, XRD and SEM. The highest chitin (20.17 ± 1.58 g) and chitosan (14.81 ± 2.05 g) yields were obtained from SQ4 (DC-DP-DM-DA). In addition, results of other important characteristics of chitosan such as solubility and degree of deacetylation (DDA); reported as 68.34 ± 2.64% and 82.30 ± 3.01% respectively were also highest in SQ4. The smooth and non-porous P. monodon chitosan with high solubility and DDA (especially SQ4) is most suitable in wastewater treatment, however not fit in medicine as filler due to its poor flowability.