Insight into immobilization efficiency of Lipase enzyme as a biocatalyst on the graphene oxide for adsorption of Azo dyes from industrial wastewater effluent

Abstract

Immobilization of enzymes improves their stability, performance, reusability, and recovery. This study investigated the removal of Azo dyes from industrial wastewater effluent using immobilized Lipase enzyme on Graphene Oxide (GO) in batch mode. The Lipase enzyme extracted from Porcine Pancreas was immobilized onto the GO via adsorption, where the enzymes are attached to the support by intermolecular forces. This study aims to investigate the immobilization efficiency of Lipase on the GO and determine the effect of parameters such as Lipase concentration, pH, and temperature on the enzyme activity. The results showed that the enzyme activity increased with the Lipase concentration, pH and temperature until an optimum point was achieved. The saturation of support surface pores causes the loss of enzyme activity due to the excessive Lipase enzyme, structural deformation of the support surface and enzyme denaturation due to extreme pH and temperature. The immobilized Lipase activity and free Lipase activity were compared. The optimum Lipase concentration is 6 mg/mL, with the greatest immobilization efficiency and highest enzyme activity. Besides, the optimum pH for the highest immobilized Lipase activity is 8.0, and the optimum temperature is 40 °C. The characterization results confirmed the immobilization of the Lipase enzyme. Adsorption isotherm and kinetic studies are also carried out to investigate the dye removal performances. The highest Azo dye removal efficiency obtained is 89.47% at 240 min of contact time and 5 mg/L of initial dye concentration. Further, the reusability of the immobilized Lipase was also investigated and found that the immobilized Lipase can be reused up to four cycles. Thus, the adsorption of dyes through immobilized lipase on GO can significantly impact various industrial sectors.