Polydopamine Coated Sawdust as a Support for Lipase Immobilization: a Sustainable Strategy for Oily Wastewater Bioremediation

The swift expansion of the edible oil industry has caused a significant increase in oily wastewater production, posing serious environmental challenges. This study explores the immobilization of Candida rugosa lipase (CrL) on polydopamine-coated sawdust (PD/SD) through covalent bonding, employing Michael addition reactions or the formation of Schiff base to yield CrL/PD/SD. Both free and immobilized CrL demonstrated optimal catalytic activity at pH 8 and 40°C; however, the immobilized enzyme demonstrated enhanced stability across a broader range of pH and temperature. Notably, immobilized CrL retained 51% of its original activity at 70°C, whereas free CrL dropped to 8% under identical conditions. Kinetic parameters for both enzyme forms were systematically analyzed. Additionally, the immobilized CrL exhibited excellent reusability, preserving 43% of its initial activity after sixteen recurrent catalytic cycles. Both free and immobilized CrL effectively hydrolyzed various edible oils, displaying comparable activity trends, although the immobilized form achieved superior hydrolysis yields. Collectively, these findings underscore the potential of CrL/PD/SD as a sustainable and efficient biocatalyst for the remediation of oily wastewater.