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Ethyl esters of babassu oil were synthesized by alkaline catalysis to make the green production of biodiesel feasible with simple methods and available technology. Babassu oil is a transparent, light yellow oil extracted from the seeds of the babassu palm (Orbinya sp), and due to its high saturated fatty acid composition (83%), it is considered a non-inedible oil. Transesterification using ethanol represents a valid alternative to using methanol because of ethanol's lower toxicity and the higher yield on weight compared to methanol. Statistical methodology was applied to optimize the transesterification reaction, which was promoted by ultrasonic waves and mechanical agitation. Nuclear magnetic resonance spectroscopy was used to quantify the conversion attained. Alkaline transesterification assisted by ultrasound produced the best results with respect to reaction time and the phase separation step. The model obtained showed that conversions higher than 97% may be achieved in 10min with correct tuning of the process variables.

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O polímero híbrido derivado de siloxano e quitosana foi obtido pela técnica sol-gel, tendo como precursor o tetraetilortosilicato (TEOS). O suporte híbrido obtido foi modificado quimicamente com epicloridrina e utilizado para imobilizar lipase de Burkholderia cepacia. O híbrido SiO 2 -quitosana deu origem a uma nova estrutura macromolecular na qual as partículas inorgânicas encontramse dispersas em escala nanométrica na matriz orgânica e ligadas à matriz por meio de ligações covalentes. Foi realizado um estudo comparativo entre a lipase livre e a imobilizada quanto à influencia do pH e temperatura, parâmetros cinéticos e estabilidade térmica. O pH ótimo para a atividade máxima de hidrólise da lipase imobilizada foi de 6,1, enquanto que para a lipase livre foi de 7,0. A temperatura ótima permaneceu em 50 ºC mesmo depois da imobilização. Os perfis de estabilidade térmica indicaram que o processo de imobilização foi favorável à estabilização da enzima e o derivado epóxi SiO 2 -quitosana foi cerca de 30 vezes mais estável que a lipase livre a 60 ºC.A hybrid polymer derived from siloxane and chitosan was obtained by sol-gel technique using tetraethoxysilane (TEOS) as a precursor. The hybrid support was chemically modified with epichlorohydrin and used to immobilize lipase from Burkholderia cepacia. The hybrid SiO 2 -chitosan formed new macromolecular structure in which the inorganic particles are dispersed at the nanometer scale in the organic host matrix and bounding through covalent bonds. A comparative study between free and immobilized lipase was provided in terms of pH, temperature, kinetic parameters and thermal stability. The pH for maximum hydrolysis activity shifted from 7.0 for the soluble lipase to 6.1 and the optimum temperature remained at 50 °C after immobilization. The patterns of heat stability indicated that the immobilization process provided the stabilization of the enzyme and the epoxy SiO 2 -chitosan derivative was almost 30-fold more stable than soluble lipase at 60 °C.