Application of gamma radiation and physicochemical treatment to improve the bioactive properties of chitosan extracted from shrimp shell

Abstract

The aim of this study is to exploit a suitable chitosan extraction method from the chitin of indigenous shrimp shells by employing different physicochemical treatments and to improve different bioactive properties of this extracted chitosan (CS) by applying gamma radiation. Chitin was prepared from shrimp shell by pretreatment (deproteination, demineralization and oxidation). Chitosan was extracted from chitin by eight different methods varying different physicochemical parameters (reagent concentration, temperature and time) and assessed with respect to the degree of deacetylation, requirement of time and reagents. The method where chitin was repeatedly treated with 121°C for 30 min with 20 M NaOH, produced the highest degree of deacetylation (DD) value (92%) as measured by potentiometric titration, with the least consumption of time and chemicals, and thus, selected as the best suitable extraction method. For further quality improvement, chitosan with highest DD value was irradiated with different doses (i.e., 5, 10, 15, 20 and 50 kGy) of gamma radiation from cobalt-60 gamma irradiator. As the radiation dose was increased, the molecular weight of the wet irradiated chitosan, as measured by the viscosimetric method, decreased from 1.16 × 105 to 1.786 × 103, 1.518 × 103, 1.134 × 103, 1.046 × 103 and 8.23 × 102 dalton, respectively. The radiation treatment of chitosan samples increased the antimicrobial activity significantly in concentration dependent manner on both gram-positive (Staphylococcus aureus) and gram-negative (Escherichia coli) bacteria, as determined by the well-diffusion method. Four to five percent wet chitosan treated with a radiation dose range of 5.0–10.0 kGy rendered the highest antimicrobial activity with least energy and time consumption. Solubility, water binding capacity (WBC) and fat binding capacity (FBC) also improved due to irradiation of chitosan.

Physicochemical Properties of Chitosan Extracted from <i>Pleurotus ostreatus</i> and Improvement of its Antibacterial Activity by Gamma Radiation

“…Results from this study corroborate with the previous study where antibacterial activity of chitosan extracted from shrimp shells was increased as the irradiation dose increased up to a certain level 29 . A limited dose level decreased the molecular weight of chitosan in such a way that might have caused the increased membrane permeability of bacterial cells and thus inhibit their growth 13,16 .…”

Antioxidant activity of gamma cobalt-60 irradiated chitosan and vitamin E combination to lead acetate-induced rats

“…Irradiated chitosan will bind free radicals from Pb 2+ ions in bodily fluid. The results itself are in accordance with Garcia et al (2015) and Aktar et al (2017). Since the free radicals are bound to irradiated chitosan, the ions will be more stable and cause less oxidative effects on the body.…”

“…Irradiated chitosan has a higher bioactivity compared to nonirradiated chitosan. This is proven by a significant increase in antimicrobial activity, both in gram-negative (Escherichia coli) and gram-positive (Staphylococcus aureus) bacteria (Aktar, Hasan, Afroz, Rashid, & Pramanik, 2017). As the molecular weight reduces, chitosan will have a higher chelating activity on blood Pb 2+ ions and a higher bioactivity as an antioxidant.…”

Synthesis and Characterization of Low Molecular Weight Irradiated Chitosan in Various Water Levels and Gamma-Ray Doses

“…Gamma irradiation helps the formation of OH radicals through radiolysis of water (H2O). This causes the molecular weight of wet chitosan to be degraded at a higher rate than dry chitosan 15 . In previous research, the addition of hydrogen peroxide (H2O2) was carried out to increase the amount of OH radical formation, apart from water.…”