Extraction and Characterization of Chitosan from the Shell Wastes of Indian Shrimp Using Different Methods of Deacetylation

Abstract

Objectives: Shrimps are a good source of chitosan, a deacetylated form of chitin, which has several medical and industrial applications. We aimed to convert waste shrimp shells to high-value chitosan product. Methods: The waste shells of the Indian shrimp, Fenneropeanus indicus were collected from Ukkadam market, Coimbatore, India, and they were subjected to demineralisation, deproteination, and deacetylation under different concentrations of NaOH, at varying temperatures. The derived chitosan was named as LAHT SCS (low alkali high temperature shrimp chitosan), HAHT SCS (high alkali high temperature shrimp chitosan), or HART SCS (high alkali room temperature shrimp chitosan), based on the treatment. Findings: The extracted chitosan samples were evaluated for physical characteristics such as moisture, ash content, and degree of deacetylation (DD). In addition, they were subjected to Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD) analysis. The HAHT SCS sample was completely soluble in 1% acetic acid and the degree of deacetylation (DD) was higher than that of standard chitosan; the crystallinity was 71%. Therefore, the extraction method employing a higher concentration of alkali (60%) and a higher deacetylation temperature (120◦C) for a long duration enhanced the solubility, conferred a higher DD (>70%), a higher crystallinity index (>60%), and less amount of ash content; all these indicate the higher quality of the sample. Among the three samples, HAHT SCS is promising for pharmaceutical and other medical applications. Novelty: The extraction of good quality chitosan from the Indian shrimp wastes was standardized. The chitosan has medicinal and industrial applications. In addition, this would reduce the pollution from improperly discarded shrimp wastes. Keywords: CrI; Chitosan; Chitin; Shrimp; Degree of deacetylation; X-ray diffraction; Fourier transform infrared spectroscopy