Biopolymer Production from Tenebrio molitor Farming Waste: A Circular Approach to Chitin and Chitosan Extraction

This study presents a circular valorization strategy for Tenebrio molitor (TM) farming residues through the production of high value biopolymers : chitin and chitosan. All insect farming waste streams, including larval and adult residues, were subjected to an optimized extraction protocol. An initial process (P1) was developed to recover chitin from both exuviae and adult cuticle. However, spectroscopic and morphological characterizations revealed the presence of lipid residues in the extracted chitin particularly in larval materials affecting its physicochemical integrity. A delipidation step was therefore introduced to purify the material and obtain α-chitin of higher structural quality. Building on these findings, an improved and simplified protocol (P2) was developed to enable more efficient recovery. This process allowed the extraction of pure, delipidated, and highly deproteinized α-chitin, closely resembling the native structure. Chitin yields ranged from 27.0% to 27.5% for the two larval exuviae stages and reached 30.0% for the adult residues. The extracted biopolymers were then converted into chitosan by N-deacetylation using Kurita’s and Broussignac’s methods, resulting in highly deacetylated chitosan (2% ≤ DA ≤ 12%) with controlled viscometric molar masses (Mv). Comprehensive structural and physicochemical characterizations were performed using FTIR, XRD, SEM, ¹H NMR, and viscosimetry. These analyses confirmed the purity, molecular integrity, and functionality of the obtained biopolymers.Due to their versatile chemical and biological properties, these materials hold strong potential for applications in cosmetics, biomedicine, and wastewater treatment supporting a sustainable circular bioeconomy.