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In this communication, lipase A from Candida antarctica (CALA) was immobilized by covalent bonding on magnetic nanoparticles coated with chitosan and activated with glutaraldehyde, labelled CALA-MNP, (immobilization parameters: 84.1% ± 1.0 for immobilization yield and 208.0 ± 3.0 U/g ± 1.1 for derivative activity). CALA-MNP biocatalyst was characterized by X-ray Powder Diffraction (XRPD), Fourier Transform Infrared (FTIR) spectroscopy, Thermogravimetry (TG) and Scanning Electron Microscope (SEM), proving the incorporation of magnetite and the immobilization of CALA in the chitosan matrix. Besides, the immobilized biocatalyst showed a half-life 8–11 times higher than that of the soluble enzyme at pH 5–9. CALA showed the highest activity at pH 7, while CALA-MNP presented the highest activity at pH 10. The immobilized enzyme was more active than the free enzyme at all studied pH values, except pH 7.

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Residual oil from babassu (Orbignya sp.), a low-cost raw material, was used in the enzymatic esterification for biodiesel production, using lipase B from Candida antarctica (Novozym® 435) and ethanol. For the first time in the literature, residual babassu oil and Novozym® 435 are being investigated to obtain biodiesel. In this communication, response surface methodology (RSM) and a central composite design (CCD) were used to optimize the esterification and study the effects of four factors (molar ratio (1:1–1:16, free fatty acids (FFAs) /alcohol), temperature (30–50 °C), biocatalyst content (0.05–0.15 g) and reaction time (2–6 h)) in the conversion into fatty acid ethyl esters. Under optimized conditions (1:18 molar ratio (FFAs/alcohol), 0.14 g of Novozym® 435, 48 °C and 4 h), the conversion into ethyl esters was 96.8%. It was found that after 10 consecutive cycles of esterification under optimal conditions, Novozym® 435 showed a maximum loss of activity of 5.8%, suggesting a very small change in the support/enzyme ratio proved by Fourier Transform Infrared (FTIR) spectroscopy and insignificant changes in the surface of Novozym® 435 proved by scanning electron microscopy (SEM) after the 10 consecutive cycles of esterification.

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.

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In this communication, it was evaluated the production of fatty acid ethyl ester (FAAE) from the free fatty acids of babassu oil catalyzed by lipase from Rhizomucor miehei (RML) immobilized on magnetic nanoparticles (MNP) coated with 3-aminopropyltriethoxysilane (APTES), Fe 3 O 4 @APTES-RML or RML-MNP for short. MNPs were prepared by co-precipitation coated with 3-aminopropyltriethoxysilane and used as a support to immobilize RML (immobilization yield: 94.7 ± 1.0%; biocatalyst activity: 341.3 ± 1.2 U p−NPB /g), which were also activated with glutaraldehyde and then used to immobilize RML (immobilization yield: 91.9 ± 0.2%; biocatalyst activity: 199.6 ± 3.5 U p−NPB /g). RML-MNP was characterized by X-Ray Powder Diffraction (XRPD), Fourier Transform-Infrared (FTIR) spectroscopy and Scanning Electron Microscope (SEM), proving the incorporation and immobilization of RML on the APTES matrix. In addition, the immobilized biocatalyst presented at 60 • C a half-life 16-19 times greater than that of the soluble lipase in the pH range 5-10. RML and RML-MNP showed higher activity at pH 7; the immobilized enzyme was more active than the free enzyme in the pH range (5-10) analyzed. For the production of fatty acid ethyl ester, under optimal conditions [40 • C, 6 h, 1:1 (FFAs/alcohol)] determined by the Taguchi method, it was possible to obtain conversion of 81.7 ± 0.7% using 5% of RML-MNP.

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