A new approach for the preparation of chitosan from γ-irradiation of prawn shell: effects of radiation on the characteristics of chitosan

• Published in: Polymer international Vol. 61; no. 8; pp. 1302 - 1308
• Main Authors: Rashid, Taslim Ur, Rahman, Mohammed Mizanur, Kabir, Shahriar, Shamsuddin, Sayed M, Khan, Mubarak A
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 01.08.2012; Wiley
• Subjects: antimicrobial activity; Applied sciences; Binding; Chitin; Chitosan; Exact sciences and technology; fat binding capacity; Irradiation; Molecular weight; Physicochemistry of polymers; Polymer industry, paints, wood; prawn shell; Prawns; Shells; Technology of polymers; Thermal properties; γ-irradiation; Biological properties; Thermomechanical properties; Chitin; antimicrobial activity; prawn shell; Antimicrobial agent; Bactericidal effect; Thermal properties; Binding capacity; Gamma radiation; Deacetylation; Morphology; Preparation; Oside polymer; Chitosan; fat binding capacity; γ-irradiation
• ISSN: 0959-8103; 1097-0126
• DOI: 10.1002/pi.4207

Chitosan is a biodegradable polymer composed of randomly distributed β‐(1,4)‐linked D‐glucosamine (deacetylated unit) and N‐acetyl‐D‐glucosamine (acetylated unit). It is produced commercially by deacetylation of chitin, which is the structural element in the exoskeleton of crustaceans (such as crabs and shrimps) and the cell walls of fungi. In the work reported, we developed a facile technique for the preparation of chitosan by irradiating prawn shell at various intensities from 2 to 50 kGy. It was observed that γ‐irradiation of prawn shell increased the degree of deacetylation (DD) of chitin at a relatively low alkali concentration during the deacetylation process. Among the various irradiation doses applied to prawn shell, a dose of 50 kGy and 4 h heating in 50% NaOH solution yielded 84.56% DD while the chitosan obtained from non‐irradiated prawn shell with the same reaction conditions had only 74.70% DD. In order to evaluate the effect of γ‐irradiation on the various physicochemical, thermomechanical and morphological properties, the chitosan samples were again irradiated (2–100 kGy) with γ‐radiation. Molecular weight, DD, thermal properties with differential scanning calorimetry and thermogravimetric analysis, particle morphology by scanning electron microscopy, water binding capacity (WBC), fat binding capacity (FBC) and antimicrobial activity were determined and the effects of various γ‐radiation doses were assessed. The DD, WBC, FBC and antimicrobial activity of the chitosan were found to improve on irradiation. It was obvious that irradiation caused a decrease of molecular weight from 187 128 to 64 972 g mol−1 after applying a radiation dose of 100 kGy which occurred due to the chain scission of chitosan molecules at glycosidic linkages. The decrease of molecular weight increased the water solubility of the chitosan, the extent of which was explored for biomedical applications. Copyright © 2012 Society of Chemical Industry Ionizing radiation can produce electronic excitation as well as ions and may also produce ions and free radicals in excited states. γ‐Irradiation of chitosan causes crosslinking and degradation due to main‐chain scission and thus its molecular weight decreases significantly and water solubility increases.