Sustainable valorization of insect processing by products via enzymatic assisted extraction of chitin

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.