Extraction and Purification of Chitin and Chitosan from Portunus pelagicus Crab Shell Waste
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Date
2021
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Publisher
Uva Wellassa University of Sri Lanka
Abstract
Crab (Portunus pelagicus) shell waste is highly accumulated in Sri Lankan seafood processing
factories, but not many efforts have been taken on utilizing it for commercial level chitin and
chitosan extraction with a higher percentage purity. Therefore the objective of this study was to
modify and develop a scale-up, simple, and high-yielding chemical method for extraction and
purification of chitin and chitosan from locally underutilized Portunus pelagicus crab shell waste. A
modified process including pre-demineralization (acetic acid), demineralization (citric acid),
deproteinization (NaOH), decolourization (n-butanol) deacetylation (NaOH), and purification
(EDTA and SDS) was optimized to obtain a new combination of treatments. Pre-demineralization
was introduced as a new step when developing the process. Citric acid was found as the best
alternative organic acid to replace HCl in demineralization. The final product was characterized by
X-Ray Diffraction (XRD) Spectroscopy and Fourier Transform Infrared (FTIR) Spectroscopy and
various physicochemical and functional properties were analyzed. Control chitin and chitosan
samples were produced using a conventional method for comparison. The yields of crude chitin,
crude chitosan, and purified chitosan were 32.52±0.68%, 26.28±0.47%, and 21.78±0.34%
respectively whereas in the control chitin and chitosan the yields were 20.34±0.72% and
13.79±0.93% respectively (p<0.05). Percentage purity of the final product on a weight basis was
82.54±1.73% with a degree of deacetylation of 85.84±2.45%. The XRD data revealed that chitosan
extracted from the developed methodology is a semi-crystalline compound with two characteristic
crystalline peaks at 2θ =9.05° and 19.1° and Crystallinity Index of 67.22%. FTIR analysis revealed
that developed chitosan was comparable with control chitosan. Chitosan produced from the
developed method showed higher results in physicochemical parameters namely moisture
(5.27±0.39%), ash (1.95±0.22%) whiteness index (72.37±0.66%), and functional properties namely
water binding capacity (318.74±0.48%), fat binding capacity (351.663±0.69%) DPPH free radical
scavenging activity (61.12±0.59%) and ferrous chelating activity (40.19±0.47%) compared with the
control (p<0.05). Developed chitosan had no antimicrobial activity for Salmonella and Micrococcus
but showed positive antimicrobial activity against locally isolated Escherichia coli at 2.5mg/ml.
Thus the developed methodology can be used to obtain high purity and high-quality chitosan with
better physicochemical and functional properties from crab shell waste
Keywords: Portunus pelagicus; Shell waste; Chitosan; Pre-demineralization; XRD; Percentage
purity
Description
Keywords
Science and Technology, Food Science, Food Science and Technology, Seafood, Animal Sciences