Biodiesel 1 Biodiesel preparation 1 Biodiesel production 1 Catalytic performance 1 Chemical stability 1 Composite materials 1 Covalent organic frameworks 1 Enzyme activity 1 Enzyme immobilization 1 External magnetic field 1 Iron oxides 1 Isomers 1 Jatropha curcas 1 Lipase immobilization Magnetism 1 Magnetite 1 Optimized conditions 1 Recovery 1 Rhizomucor miehei 1 Rhizomucor miehei lipase 1 Synthetic fuels 1 alternative energy 1 biofuel 1 catalysis 1 enzyme activity 1 immobilization 1 magnetic field 1