Sonication-assisted extraction of chitin from North Atlantic shrimps (Pandalus borealis).

The influence of sonication during extraction of chitin from North Atlantic shrimp (NAS) shells (Pandalus borealis) on chitin yield, purity, and crystallinity was investigated. Shells were peeled, washed, lyophilized, ground, and suspended for 4 h in 0.25 M HCl (1:40) at 40 degrees C followed by ultrasonication at 41 W/cm(2) for 0, 1, and 4 h, respectively. Demineralized shells were lyophilized, resuspended in 0.25 M NaOH (1:40), and ultrasonicated at 41 W/cm(2) for 0, 1, and 4 h to remove proteins. The yield and mineral and protein contents were determined after each processing step. The purity of extracted chitin was determined from the total amount of glucosamine. The crystallinity index and size of crystals were calculated from wide-angle X-ray scattering measurements. Scanning electron microscope images were recorded to evaluate morphological changes in samples. The yield of chitin from NAS decreased from 16.5 to 11.4% for 0 and 1 h sonicated samples, respectively, which was attributed to increased concentrations of depolymerized materials in the wash water. Sonication did not enhance the removal of minerals. The application of ultrasound enhanced the removal of proteins from 39.8 to 10.6, 8.3, and 7.3% after 0, 1, and 4 h of sonication treatments. The crystallinity index of chitin decreased from 87.6 to 79.1 and 78.5% after 1 and 4 h of sonication, yielding chitosans with crystallinity indices of 76.7, 79.5, and 74.8% after deacetylation, respectively. Fourier transform infrared spectroscopy scans indicated that the degree of acetylation of chitins was unaffected by sonication. Comparison of the extraction results of NAS with that from freshwater prawns indicated that more impurities were left in NAS chitin, suggesting that composition and structural arrangement of chitin in shells influence the efficiency of ultrasound-assisted extraction.

Sonication-assisted extraction of chitin from shells of fresh water prawns (Macrobrachium rosenbergii).

The effect of sonication during chitin extraction from freshwater prawn shells on yield, purity, and crystallinity of chitin was investigated. Dry prawn shells were suspended for 4 h in 0.25 M HCl at 40 degrees C while they were sonicated for 0, 1, and 4 h. Demineralized shells were lyophilized, resuspended in 0.25 M NaOH, and sonicated again for 0, 1, and 4 h for protein removal. The yield of chitin decreased from 8.28 to 5.02% for nonsonicated and sonicated samples, respectively, which was attributed to losses of depolymerized materials in the wash water. The application of ultrasound enhanced the removal of proteins. In nontreated shells, the amount of protein was 44.01% and was reduced to 12.55, 10.59, and 7.45% after 0, 1, and 4 h of sonication treatments. The glucosamine content slightly decreased with sonication probably because of losses due to depolymerization. The crystallinity indices of chitins decreased as the time of sonication increased. The degree of acetylation of chitins was unaffected by sonication, but the degree of acetylation of chitosans produced from sonicated chitin decreased from 70.0 to 68.7 and 61.4% for 1 and 4 h sonicated samples, respectively.