Covalent immobilization of lipase on magnetic biochar for one-pot production of biodiesel from high acid value oil

Magnetic biochar was synthesized via chelation of Fe3+ with carboxymethyl cellulose and pyrolysis for covalently immobilizing Eversa® Transform lipase. The magnetic biochar had 75.8 mg/g lipase loading that was 54.1 % higher than that without magnetism. The immobilized lipase achieved 91.3 mg/g lipase loading with 19.2 U/mg lipase activity after optimization. It showed good thermal and acid stability with 82.5 % and 98.2 % relative activity at 45 °C and pH 4, respectively. Its relative activity was 90.8 % after stored for 30 d at 4 °C. After magnetically separated for 10 cycles, it still kept 70.1 % activity due to the strong covalent bonding. The lipase further catalyzed one-pot esterification and transesterification of high acid value oil (38 mg KOH/g) with 95.7 % biodiesel yield and cycled for 10 times at 85.7 % yield. Kinetic study gave the activation energy of 28.7 kJ/mol. The covalently immobilized lipase could find practical applications.