Extraction and characterization of chitosan from local fish scales in Bangladesh

Chitosan is a versatile biopolymer derived from chitin, and it is widely used in biomedicine, food preservation, environmental applications, and tissue engineering. In this study, an attempt was made to extract chitosan from locally available fish scale biowaste in Bangladesh, namely Rui ( Labeo rohita ) and Hilsa ( Tenualosa ilisha ). The extraction process consisted of pre-treatment, demineralization, deproteinization, and alkaline deacetylation. Characterization of structural and physicochemical properties was done by Fourier Transform Infrared (FTIR) spectroscopy, Scanning Electron Microscopy (SEM) and X-ray Diffraction (XRD). FTIR identified amino, hydroxyl, and acetyl functional groups, and the SEM images demonstrated a porous structure that is preferable for biomedical applications. XRD analysis indicated partial crystallinity as evidenced by distinct XRD peaks for both species. The XRD found strong reflections at 25.93°, 31.79°, 34.02°, and 49.57° for Hilsa-derived chitosan, and 25.94°, 31.9°, 39.86°, and 49.57° for Rui-derived chitosan. The extraction yield was 16.97 % for Hilsa and 19.43 % for Rui. On the other hand, the degrees of deacetylation were 71.2 % and 76.5 %, respectively, compared to 89.5 % in commercial chitosan. These results suggest that fish scale biowaste can serve as a sustainable and cost-effective source of chitosan, with intriguing potential for biological, pharmacological, and environmental applications.