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Since chitin is closely associated with proteins, deproteinization is a crucial step in the process of extracting chitin. Thus, this research aimed to extract chitin from Portunus segnis and Penaeus kerathurus shells by means of crude digestive alkaline proteases from the viscera of P. segnis , regarding deproteinization step, as an alternative to chemical treatment. Casein zymography revealed that five caseinolytic proteases bands exist, suggesting the presence of at least five different major proteases. The optimum pH and temperature for protease activity were pH 8.0 and 60 °C, respectively, using casein as a substrate. The crude enzymes extract was highly stable at low temperatures and over a wide range of pH from 6.0 to 12.0. The crude alkaline protease extract was found to be effective in the deproteinization of blue crab and shrimp shells, to produce chitin. The best efficiency in deproteinization (84.69 ± 0.65% for blue crab shells and 91.06 ± 1.40% for shrimp shells) was achieved with an E/S ratio of 5 U/mg of proteins after 3 h incubation at 50 °C. These results suggest that enzymatic deproteinization of crab and shrimp wastes by fish endogenous alkaline proteases could be a potential alternative in the chitin production process. [ABSTRACT FROM AUTHOR]

Abstract: Three marine sources of chitin from Tunisia were investigated. Structural differences between α-chitin from shrimp (Penaeus kerathurus) waste, crab (Carcinus mediterraneus) shells, and β-chitin from cuttlefish (Sepia officinalis) bones were studied by the 13C NMR, FTIR, and XRD diffractograms. The 13C NMR analysis showed a splitting of the C3 and C5 carbon signals for α-chitin, while that of β-chitin was merged into a single resonance. The bands contour of deconvoluted and curve-fit FTIR spectra showed a more detailed structure of α-chitin in the region of O H, N H and CO stretching regions. IR and 13C NMR were used to determine the chitin degree of acetylation (DA). XRD analysis indicated that α-chitins were more crystalline polymorph than β-chitin. Shrimp chitin was obtained with a good yield (20% on raw material dry weight) and no residual protein and salts. Chitosans, with a DA lower than 20% and relatively low molecular masses were prepared from the wet chitins in the same experimental conditions. They were perfectly soluble in acidic medium. Nevertheless, chitin and chitosan characteristics were depending upon the chitin source. [Copyright &y& Elsevier]

The effects of sepia ink (Sepia officinalis) extract solutions with concentrations of 0.0%, 0.01%, 0.2% and 2% on the microbial flora and the chemical composition of stored peeled shrimp (Penaeus kerathurus) were examined at two temperatures (-2 and 0 ° C). The quantification of aerobic and psychotrophic bacteria was performed by a plate count after each 3 days of storage. Results showed that partial freezing and coating treatments had synergistic effects in reducing the aerobic plate counts (APCs) with at least a 10-day extension of shelf life. The inhibition efficacy on the psychotrophic cells in shrimp meat increased with the increase in concentration of the added extract. However, the extract showed no effect after 16 days on the mesophilic bacteria. No detrimental effects of sepia coating on organoleptic parameters such as appearance, odour, and taste were observed. Partial freezing reduced significantly the formation of nitrogenous compounds in all samples, however total volatile bases (TVB) and trimethylamine (TMA) levels were lower in the sepia extract-treated samples. Initially, shrimp tissue ninhydrin positive substances (NPS) level was 9.74 ± 1.05 mM/100 g tissue. No significant change was observed in the treated-samples during the refrigerated storage, conversely, these concentrations increased in the raw shrimps. [Copyright &y& Elsevier]