<p>Catalase (CAT) is a critical antioxidant enzyme widely used in industrial and agricultural applications due to its ability to decompose hydrogen peroxide (H₂O₂) into water and oxygen. However, its practical use is often hindered by issues such as low stability and reusability. In this study, CAT was effectively immobilized onto the onion inner epidermis (OIE) via adsorption and cross-linking techniques, aiming to improve its catalytic activity, stability and reusability. The optimization of the immobilization process was carried out by evaluating key factors, including CAT concentration, OIE quantity, adsorption duration, and cross-linker concentration. The immobilized CAT exhibited a significant improvement in thermal stability, retaining 50% activity at 60&#xa0;°C compared to 30% for the free enzyme. Similarly, it displayed enhanced pH stability, maintaining 70% activity at pH 5.5 and pH 8.5, while the free enzyme retained only 50% and 60%, respectively. Kinetic studies revealed a higher V_max (2.26 × 10⁻⁴ µmol H₂O₂/min) and lower K_m (3.36 mM) for the immobilized enzyme, indicating improved catalytic efficiency and substrate affinity. The immobilized enzyme preserved 40% of its activity after 28 consecutive uses and retained 30% activity following 30 days of storage, demonstrating its long-term stability. This study demonstrates that immobilized CAT on OIE is a promising biocatalyst for agricultural and food industries, where it can be utilized for H₂O₂ detoxification, food preservation, and wastewater treatment. The use of OIE as a low-cost, natural carrier further supports the development of sustainable and eco-friendly biocatalytic systems for industrial applications.</p> Graphical Abstract <p></p>