Processing residues from adult Tenebrio molitor were evaluated as a sustainable source of chitin and chitosan through an optimized enzyme-assisted extraction strategy. Preliminary proximate analysis revealed a high chitin fraction and low mineral content, confirming the suitability of the biomass for biopolymer recovery. The enzymatic deproteinization process was compared with a conventional chemical method to assess purification performance. Process parameters were optimized using a Face-Centered Central Composite Design, investigating the combined influence of pH, enzyme concentration, and extraction time, achieving deproteinization efficiencies ranging from 86.1% to 94.1% approaching those obtained by the chemical reference process. Enzyme-extracted chitin showed low residual lipids (0.9–4.8 g/100 g) and minimal ashes (0–0.5 g/100 g), and approximately 7% moisture. ATR-FTIR analysis confirmed the presence of characteristic chitin functional groups; while SEM analysis revealed porous microfibrillar morphology consistent with effective protein removal and structural integrity. Chemical deacetylation of the extracted chitin yielded chitosan with a degree of deacetylation of 85%, and FTIR spectrum overlapped with that of a commercial reference, indicating comparable structural features. TGA displayed a typical multi-stage degradation pattern, including initial moisture loss, major polymer decomposition above 230 °C, and a low residual ash fraction (∼2%). Furthermore, the recovered chitosan exhibited a water-binding capacity of 773% ± 19 and a fat-binding capacity of 715% ± 12. Overall, the DoE-optimized enzymatic process enables efficient valorization of insect processing side streams, producing refined chitin and chitosan while supporting environmentally sustainable and circular biorefinery strategies.
Orlandi et al. (Fri,) studied this question.