BUTTERNUT SQUASH PEELS AS A SUBSTRATE FOR THE PRODUCTION OF BIOACTIVE COMPOUNDS AND ENZYMES THROUGH SOLID STATE FERMENTATION

The processing of horticultural products generates a large amount of waste, which is usually discarded without proper treatment, causing environmental and economic impacts. This study investigated the use of butternut squash peels (Cucurbita moschata D.) as a substrate for solid-state fermentation using Aspergillus tubingensis LBA02 to obtain antioxidant compounds and hydrolytic enzymes. An experimental design (CCRD 2²) was used to evaluate the effects of initial moisture content (45-75%) and incubation temperature (25-37°C) at 48 and 72h on the followed responses: Total Phenolic Content – TPC, antioxidant activity (ABTS, DPPH, and FRAP), enzyme production (α-amylase, endo-β-1,4-glucanase, protease, and lipase), and soluble protein content. The results showed that the responses TPC (72h), DPPH (48h and 72h), α-amylase, endo-β-1,4-glucanase, lipase, and soluble protein content (48h and 72h) generated statistically significant (p<0.10) models, with coefficients of determination (R²) ranging from 0.73 to 0.99.  After 48h of fermentation, TPC ranged from 8.99 to 19.53 mg of gallic acid equivalent per gram of fermented peels (mg GAE/g), while the highest antioxidant activities were detected at 48h, reaching 134.00 µmol of Trolox equivalent per gram of fermented peels (µmol TE/g) (ABTS), 46.29 µmol TE/g (DPPH), and 69.16 µmol TE/g (FRAP). Maximum enzyme production occurred at 72h, reaching 62.63 U/g for α-amylase, 11.89 U/g for endo-β-1,4-glucanase, 94.58 U/g for protease, and 2.27 U/g for lipase. The highest soluble protein content was observed at 48h (7.65 mg/mL). The optimal conditions for the production of antioxidant compounds were achieved with moisture levels between 49.4% and 60% and temperatures ranging from 23°C to 30°C, while enzyme production was favored by moisture above 60% and temperatures between 23 and 25°C. The results demonstrated the feasibility of utilizing butternut squash peels through solid-state fermentation to simultaneously obtain antioxidant compounds and hydrolytic enzymes.