Immobilization of lipase on the graphene oxides magnetized with NiFe2O4 nanoparticles for biodiesel production from microalgae lipids

Candida rugosa lipase was immobilized on graphene oxides magnetized with NiFe2O4 nanoparticles (NiFe2O4-GO) and used for the transesterification of algal lipids. The VSM, FE-SEM, EDS, and FTIR analyses were done to investigate the features of nanoparticles, graphene oxide, and synthesized magnetic nanobiocatalyst. These tests confirmed the successful immobilization of Candida rugosa lipase on the base. Immobilization was caused via interfacial activation on hydrophobic supports. The lipase immobilization process was studied using different enzyme concentrations (30–160 µg/ml) at different incubation times (1–5 h). It was found that 100 µg/ml enzyme concentration (3.3 mg supports/ml solution) for 2 h incubation time were the best conditions which led to the immobilization efficiency of 78%. The results revealed that in comparison to the free enzyme, the immobilized enzyme is more thermal and pH resistant; it could retain 70% of its initial activity at 60 °C and lose only 20% at pH 9. Immobilized lipase retained 47% of its initial activity after 6 cycles of hydrolysis at 37 °C and pH 7, demonstrating its reusability and resistance. Biodiesel production efficiency was obtained 80% and 68% when using free and immobilized lipase as biocatalysts, respectively.