Comparison of physicochemical properties of chitins isolated from an insect (Melolontha melolontha) and a crustacean species (Oniscus asellus)

The chitin structures of two common European species belonging to Insecta (Melolontha melolontha) and Crustacea (Oniscus asellus) were isolated. The same procedure is followed for chitin isolations for both the species. First, HCl was used for removing of minerals in the organisms, and then, the protein structure was removed by using NaOH. Chitins obtained from these two species were characterized physicochemically. Physicochemical properties of chitins isolated from the insect and the crustacean were compared to each other. The chitin content for dry weights of M. melolontha and O. asellus were recorded as 13-14 and 6-7 %, respectively. The results of Fourier transform infrared spectroscopy, thermogravimetric analysis and X-ray diffraction analysis were found to be more or less similar. The surface morphologies of chitins were examined via environmental scanning electron microscopy and nanofibers, and pore structures were observed. While the chitin nanofibers of O. asellus were adherent to each other, nanofibers of M. melolontha were non-adherent. On the other hand, the number of pores was much higher in the chitin from M. melolontha than in the chitin from O. asellus. Looking at the elemental analysis results, the M. melolontha chitin was found to be more pure than the O. asellus chitin. For this reason, M. melolontha has been considered more attractive source for chitin than O. asellus.