Integrated ultrasound-assisted enzymatic extraction from grape seeds: impact on oil yield, fatty acid profile, and antimicrobial activity

Grape seeds recovered from grape marc distillation are rich in lipids, proteins, and carbohydrates, but their structured lignocellulosic matrix limits aqueous recovery of intracellular oil bodies. This study developed an extraction strategy combining ultrasound pretreatment with aqueous enzymatic hydrolysis using a pectinolytic cocktail (E1) and Alcalase® in simultaneous (SIM) or sequential (SEQ) configurations. Ultrasound pre-treatment markedly intensified the process, increasing oil recovery up to ∼17–18% within 4 h, compared to 5–6% obtained with enzymatic treatments alone. Kinetic modelling showed configuration-dependent mechanisms: SIM and US + SIM followed pseudo-first-order kinetics, with apparent rate constants of 0.332 ± 0.007 and 0.799 ± 0.011 h−1, respectively, whereas SEQ was best described by a Gompertz model (k = 1.71 ± 0.12 h−1; t0 = 2.64 ± 0.04 h) and US + SEQ by a logistic model (k = 5.72 ± 0.45 h−1; t0 = 2.36 ± 0.04 h). The process also enabled co-recovery of protein and carbohydrate fractions (8.03% and 8.15% respectively) under US + SEQ. The extracted oils retained a grape seed oil-like fatty acid profile dominated by linoleic acid, while US + SIM showed the strongest antioxidant activity, with IC50 values of 40.21 ± 0.25 μg mL−1 for DPPH and 29.39 ± 1.41 μg mL−1 for ABTS. The protein-rich fraction showed dose-dependent antimicrobial activity against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus epidermidis. Overall, this strategy provides a solvent-reduced route for grape seed fractionation, although key factors such as enzyme cost, ultrasound energy consumption, and downstream processing operations should be evaluated to unlock industrial scale implementation.