Banca de DEFESA: SINARA SILVA NEVES MACHADO

SUSTAINABLE POTENTIAL OF OBTAINING CHITIN AND CHITOSAN FROM INSECT PRODUCTION WASTE

biopolymers, insects, residues, Zophobas morio, Tenebrio molitor, Blaptica dúbia.

The production of insects on a large scale is becoming common all over the world, generating a significant amount of waste from these creations. An example are the exoskeletons resulting from the initial growth of insects (exchanges) and dead adults at the end of their life cycle. These residues are chitin sources with potential for technological and sustainable application, still little explored. Thus, this work aimed to obtain and characterize chitin and chitosan from the exoskeletons (larval stage and adult insect) of the creation of three specimens of insects, Tenebrio molitor, Zophobas morio and Blaptica dubia. The exoskeletons were separated, dried in an oven with air circulation (50ºC/12h) and kept under refrigeration (-20ºC) until analysis. For chitin extraction, a chemical method was used in three stages: demineralization, deproteinization and depigmentation. Chitosan was obtained from chitin deacetylation in sodium hydroxide solution (60% m.v-1). The chitin and chitosan samples were characterized by means of infrared spectroscopy (FTIR), thermal gravimetric analysis (TGA), X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) techniques. Chitosan was also observed for the Degree of Deacetylation (DD), solubility and rheological parameters. The yield of chitin and chitosan in percentage of dry mass of exoskeletons ranged from 11.21 to 20.89% and 6.26 to 7.07%, respectively. The sample with the lowest percentage of chitin was the exoskeleton of the larva of Zophobas morio and the one with the highest percentage was the exoskeleton of the beetle of Zophobas morio. Difractograms confirmed the obtainment of chitin and chitosan from insect residues, with the presence of α-chitin. The relative crystallinity indices (ICR) of chitin ranged from 65.9-89.2%, the TG/DTG curves showed two typical thermal events, the first being associated with moisture loss and the second with thermal decomposition of samples with Tonset from 197.70 to 427.95ºC. The chitosan samples showed ICR from 65.3 to 80.2% and the TGA curves showed Tonset between 245.80 to 329.90°C. Chitosan solutions showed a pseudoplastic behavior with apparent viscosities ranging from 195.96 to 249.86 mPa.s. The degree of deacetylation ranged from 75.75 to 89.21% and the solubility from 69.88 to 94.39%. The micrographs revealed varied surfaces including pores, roughness and fibrillar shapes, presenting similar results to commercial chitosan. In general, the characterization of biopolymers extracted from insect residues showed high similarity in relation to those obtained from conventional sources. The results of the present study reinforce the feasibility of using alternative sources of chitin and chitosan, providing the use of residues from the large-scale production of insects, contributing to sustainability.