Physicochemical, morphological and structural characterization of the chitin and chitosan of Tenebrio molitor and Galleria mellonella insects

In the present study, chitin and chitosan were isolated from flour obtained from adult specimens of Tenebrio molitor and Galleria mellonella. The yield of chitin was 11.6% and 6.2% for T. molitor and G. mellonella, respectively. The degree of deacetylation of chitosan was 80.5% and 88.5% for G. mellonella and T. molitor, respectively. The content of nitrogen (≈ 6.5%), humidity (≈ 5.8%) and ashes (≈ 0.4%) in the chitin and chitosan of both insects indicated an acceptable quality. No differences were observed between the molecular weights of the chitin (≈ 889 kDa) and the chitosan (≈ 254 kDa) of both insects. Scanning electron microscopy revealed fiber structures in the chitin and chitosan from T. molitor; in contrast, the chitin and chitosan of G. mellonella were spongy. Infrared spectroscopy and X-ray diffraction showed α-type polymorphism in the chitin of both insects. The biopolymers of G. mellonella exhibited a higher crystallinity index than those of T. molitor. Due to the higher yield obtained from T. molitor, this insect could be considered as a promising alternative source for obtaining chitin and chitosan.

Keywords: Lepidoptera, coleoptera, α-chitin, HPLC-SEC, biopolymer materials.