Abstract We applied ultrasonic technology for the transesterification of soybean oil catalyzed by a mixture of lipases (combi-lipase: 75 % Novozym 435; 10 % Lipozyme TL-IM; and 15 % Lipozyme RM-IM), verifying the effects of ultrasonic amplitude, pulse conditions, the ethanol:oil molar ratio, enzyme concentration, and the influence of solvent (tert-butanol on the reaction. We also compared this system against ultrasound combined with mechanical stirring, and the efficiency of the combi-lipase, compared with the individual use of each lipase. The optimum conditions for the transesterification reaction were determined as enzyme concentration of 15 % (in relation to oil mass); ethanol:oil molar ratio of 3:1; ultrasonic amplitude of 30 %, duty cycle of 50 % and time pulse of 15 sec. The yields of conversion of ethyl esters with and without solvent were similar, indicating that the use of solvents during enzymatic transesterification reactions is not necessary when ultrasonic technology is applied to the system. The combination of mechanical stirring and ultrasound did not improve the yields of conversion compared to ultrasonic technology alone. The proposed combi-lipase produced higher yields of ethyl esters (75 %) than the individual lipases (55 %) in 5 h under ultrasonic-assisted batch reactions.

We carried out the physico-chemical characterization of Immobead 150, a hydrophobic support for the immobilization of lipases. Thermomyces lanuginosus lipase (TLL) was immobilized on Immobead 150 by multipoint covalent attachment (ImmTLL) and the morphological, textural, structural, thermal, and physico-chemical properties of the support, before and after enzyme immobilization, were investigated. Immobead 150 presents approximately 1,000 µmol of epoxy groups per gram of support, a high hydrophobicity, and good thermal stability. The spherical particles of Immobead 150 present average diameters of 155 µm, specific surface areas of 137 m2 g-1 and pore volumes of 0.37 cm3 g-1, showing pores in the region of the micro and meso sizes. The immobilization process of TLL (150 mg g-1) caused a decrease of the specific area and pore volumes, to 63 m2 g-1 and 0.25 cm3 g-1, respectively, as a result of coating of the support surface by the enzyme molecule. However, the immobilization process did not affect the morphology of the support. The obtained biocatalyst was effective for the syntheses of fatty acid ethyl esters (biodiesel), and of aroma esters, showing yields of 68 and 70%, respectively, similar to commercial preparations used as controls.