Biotechnological valorization of Tenebrio molitor through solid-state fermentation with Aspergillus oryzae: synthesis of enzymes and bioactive compounds

The consumption of insects as food is traditional in several regions of the world, mainly in Asia, but still faces cultural barriers in the West. Concerns with food security and population growth have motivated studies on edible insects, strongly driven by the Food and Agriculture Organization (FAO) since 2013. Among edible insects, Tenebrio molitor stands out for its nutritional profile, with high protein content (up to 50% dry weight), essential amino acids, fatty acids, vitamins, and minerals. Fermentation has shown potential to enhance the nutritional value of raw materials through substrate biotransformation mediated by microbial enzymes. Proteases, for instance, cleave peptide bonds, generating smaller peptides with bioactivity, improving protein digestibility, and reducing antinutritional or allergenic compounds. This study investigated the solid-state fermentation of T. molitor larvae meal using Aspergillus oryzae as inoculum, aiming at the production of hydrolytic enzymes (proteases, lipases, α-amylases) and the evaluation of antioxidant properties (ABTS, DPPH, FRAP). Fermentation was conducted under optimized conditions: initial moisture 42%, incubation temperature 30 °C, and inoculum 1 × 10⁷ spores/g. Samples were analyzed at 0, 24, 48, 72, and 96 h. Enzymatic activity increased progressively, reaching maxima at 72 h for proteases (691.73 U/g) and α-amylases (14,065.3 U/g), and at 96 h for lipases (39.09 U/g). Productivity was highest in the first 24 h for lipases (0.81 U/g×h) and α-amylases (373.42 U/g×h), while protease productivity peaked at 48 h (14.07 U/g×h). Antioxidant capacity also improved during fermentation. By ABTS and DPPH assays, maximum activities occurred at 48 h, with values of 1030.89 and 405.84 µmol TE/g, corresponding to increases of 55.26% and 94.68%, respectively. In the FRAP assay, the greatest increase was observed at 96 h (403.2 µmol TE/g), equivalent to a 258.97% rise. Overall, fermentation of T. molitor with A. oryzae enabled simultaneous production of enzymes of industrial interest and enhanced antioxidant properties, effects linked to protein biotransformation and bioactive peptide release. At 48 h, protease productivity coincided with the strongest antioxidant activities (ABTS and DPPH), highlighting the close relationship between enzymatic hydrolysis and functional compound generation. These results demonstrate that solid-state fermentation is a promising strategy for valorizing edible insects, expanding their application in functional foods and bioactive ingredients.