Preparation and properties of chitosan microspheres from giant black tiger shrimp Penaeus monodon shell

Abstract

Chitosan has been prepared from shrimp shells. The molecular weight and per cent deacetylation have been determined to be 2.67 x 10[superscript 5] kDa and 69 - 76%, respectively. The ash and moisture were 0.101%(SD 0.08%) and 13% (SD 3.35%) respectively (n=4). The yield was 42.3%(SD 7.94%, n=4). Chitosan millispheres have been prepared by mixing and stirring chitosan and triethanolamine in paraffin wax pre-dissolved with Span[superscript (R)] 80. The size of the millisphere was approximately 1.5 mm in diameter. The spheroids were clear with rough surface under scanning electron microscopy. The swelling properties of chitosan millispheres (up to 20% diameter at 360 minutes incubation) under different pH’s and ionic strengths have been explained by Tanaka’s theory of gel polymers. According to the theory, pressures acting on a polymer particle come from three sources (1) osmotic pressure (calculated by Donnan equilibrium) (2) polymer-polymer affinity (not applicable) and (3) rubber elasticity (in this case a combination of polymer "salting out" and the polar bridging of positive charges on by Span[superscript (R)]). The release of three test proteins, chymotrypsin, bovine serum albumin and protamine took about an hour to approach the peak value and declined only in the case of protamine. The effects of pH and ionic strength of the medium on protein release were explained in terms of charges on chitosan and protein molecule as well as the negative polarity of Span[superscript (R)].