Ethyl esters synthesis catalyzed by lipase B from Candida antarctica immobilized on NiFe2O4 magnetic nanoparticles

The development of heterogeneous biocatalysts allows the expansion of the application of enzymes in different industrial processes, favoring the establishment of clean technologies. This work investigates the capacity of nickel ferrite magnetic nanoparticles (NiFe₂O₄) as a support for lipase B from Candida antarctica (CalB) immobilization. The adsorption capacity of the support revealed a maximum value of 15 mg_protein/g_support, according to the Langmuir isotherm model. Efficiency immobilization by physical adsorption was low (21.3 %), and CalB was covalently immobilized after functionalization of NiFe₂O₄ with APTMS (3-aminopropyl trimethoxysilane) and activation with glutaraldehyde (GA), showing higher immobilization yield (62.9 %). The spinel ferrite NiFe₂O₄ was characterized by many physicochemical analyses. The enzyme derivatives obtained (NiFe₂O₄-CalB and NiFe₂O₄-APTMS-GA-CalB) were evaluated in the synthesis of alkyl esters. Despite no production was observed in the transesterification reactions, esterification led to 37.3 ± 1.0 % and 62.1 ± 0.2 % of oleic acid conversions using NiFe₂O₄-APTMS-GA-CalB and NiFe₂O₄-CalB, respectively. After 4 cycles, NiFe₂O₄-CalB maintained 92 % of its initial activity. Nickel ferrite magnetic nanoparticles form an efficient heterogeneous catalyst with lipase, which could be used to remove the content of free fatty acids (FFAs), like oleic acid, present in cheap raw materials to produce biodiesel.