Microwave-Assisted Pretreatment of Corncob Using Potash Alum (AlK(SO4)2) Catalyst for Enhanced Xylooligosaccharide (XOS) Extraction with High Prebiotic and Antioxidant Properties

This study explores the potential of corncob waste valorization through microwave-assisted hydrolysis for xylooligosaccharides (XOS) extraction using potash alum (AlK(SO₄)₂) as a catalyst. The process was optimized through a One-factor-at-a-time (OFAT) approach, evaluating potash alum concentration, heating time, and reaction temperature. Optimal conditions (20 µmol/mL potash alum, 5 minutes, 160°C) yielded 12.32 g/L XOS in the hydrolysate, with ethanol precipitation achieving a 16.97% (g/g) purified XOS yield. Potash alum was chosen as an alternative catalyst due to its potential cost-effectiveness and milder environmental impact compared to strong acids, though further comparative analysis is warranted. The purified XOS exhibited strong antioxidant activity (94.16 ± 0.54% DPPH radical scavenging) and high total phenolic content (32.63 ± 0.29 µg GAE/mg of XOS). In vitro prebiotic assays demonstrated XOS’s capacity to enhance probiotic growth, particularly Lactobacillus fermentum, which showed the highest prebiotic index and prebiotic activity within 24 hours. These findings suggest that corncob-derived XOS can serve as a functional ingredient with prebiotic and antioxidant properties, supporting its application in health-promoting food and nutraceuticals.