Abstract
The synthesis of ethyl butyrate catalyzed by lipases A (CALA) or B (CALB) from Candida antarctica immobilized onto magnetic nanoparticles (MNP), CALA-MNP and CALB-MNP, respectively, is hereby reported. MNPs were prepared by co-precipitation, functionalized with 3-aminopropyltriethoxysilane, activated with glutaraldehyde, and then used as support to immobilize either CALA or CALB (immobilization yield: 100 ± 1.2% and 57.6 ± 3.8%; biocatalysts activities: 198.3 ± 2.7 Up-NPB/g and 52.9 ± 1.7 Up-NPB/g for CALA-MNP and CALB-MNP, respectively). X-ray diffraction and Raman spectroscopy analysis indicated the production of a magnetic nanomaterial with a diameter of 13.0 nm, whereas Fourier-transform infrared spectroscopy indicated functionalization, activation and enzyme immobilization. To determine the optimum conditions for the synthesis, a four-variable Central Composite Design (CCD) (biocatalyst content, molar ratio, temperature and time) was performed. Under optimized conditions (1:1, 45 °C and 6 h), it was possible to achieve 99.2 ± 0.3% of conversion for CALA-MNP (10 mg) and 97.5 ± 0.8% for CALB-MNP (12.5 mg), which retained approximately 80% of their activity after 10 consecutive cycles of esterification. Under ultrasonic irradiation, similar conversions were achieved but at 4 h of incubation, demonstrating the efficiency of ultrasound technology in the enzymatic synthesis of esters.
Highlights
The catalysis of reactions mediated by biological catalysts is an alternative to traditional chemical catalysis [1,2,3]
The performance of immobilization was evaluated by recovery activity as well, presenting a value of 97.5% for catalyzed by lipases A (CALA)-magnetic nanoparticles (MNP) and 80.5% for CALB-MNP
The support used in this communication, having a high surface density of amino groups and activated with glutaraldehyde, may permit hydrophobic, anionic exchange and covalent interactions interfacial activation, which is faster than the direct covalent attachment; the use of ionic strength and detergents may ensure immobilization firstly via direct covalent attachment [51]
Summary
The catalysis of reactions mediated by biological catalysts is an alternative to traditional chemical catalysis [1,2,3]. Enzymes are biological macromolecules that reduce the occurrence of undesirable side reactions and can work under mild temperature and pressure, which minimizes the energy demand and thermal degradation of the product of interest [4,5]. In this sense, lipases (triacylglycerol hydrolases, EC 3.1.1.3) are enzymes that stand out due to the wide range of reactions that they can catalyze (e.g., hydrolysis, acidolysis, esterification, transesterification, and amination) in different media (organic solvents, ionic liquids, supercritical fluids, etc.) [6,7,8], with high stability and great diversity [9,10]. CALA has not hitherto been so widely used, even though it bears several interesting features [19]
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