Optimum Conditions for Extraction of Chitin and Chitosan from Callinectes amnicola Shell Waste

Abstract

The optimization of process variables for the extraction of chitin and chitosan from crab (Callinectes amnicola) shell waste and for the degree of deacetylation (DDA) of extracted chitosan was investigated using response surface methodology (RSM). The respective effects of four and three process parameters on the extraction yields of chitin and chitosan and on the DDA of chitosan were examined. The optimized chitin extraction conditions based on the yield (4.84 g or 19.36%) were obtained to be 3.25 M HCl solution, 18.55 h demineralization time, 2.39 M NaOH solution and 2 h deproteinization time, while the maximum chitosan yield (5.98 g or 13.29%) was obtained at modelled optimized conditions of 50% w/w NaOH solution, 85.05°C deacetylation temperature, and 133.64 min deacetylation time. The modelled optimization conditions for the highest DDA of chitosan produced from crab shell waste were 50% w/w NaOH solution, 84.46°C deacetylation temperature, and 187 min deacetylation time, with the corresponding predicted DDA of 84.20%. Excellent agreement was obtained between experimental DDA of chitosan (84.50%) and the predicted value, with the percentage error being ±0.36. Independent predicted robust quadratic models for predicting the yields of chitin and chitosan extraction and the DDA of chitosan from the crab shell waste were obtained, validated and verified.