LAUSR

Abstract The present work aimed to extract chitin and chitosan from blue crab ( Portunus segnis ) shells, via an optimized procedure keeping as much as possible its native structure. Thus, several microbial, visceral and commercial proteases were tested for their deproteinization efficiency. High levels of protein removal of about 82% and 85% were recorded using Bacillus safensis proteases and crude enzyme extract of P. segnis , respectively. Further, 0.5 M HCl baths based system was adopted for minerals removal. Blue crab chitin had the following characteristics: acetylation degree of 97%, deproteinization and demineralization rates of 92% and 100%, respectively. Subsequently, blue crab chitosan (BCC) was prepared by chitin N-deacetylation, leading to an acetylation degree of 10%. After characterization by FTIR spectroscopy and X-ray diffraction, the functional properties and antioxidant and antimicrobial activities of BCC were investigated. Interestingly, BCC exhibited notable in vitro antioxidant activity including DPPH and hydroxyl radicals scavenging, β-carotene bleaching inhibition and metal chelating effects (92%, 89%, 72%, and 93%, at 5 mg/ml, respectively). Moreover, chitosan markedly inhibited growth and adhesion of all microorganisms tested, and was efficient in the disruption of pre-formed biofilms.