Polysiloxane-polyvinyl alcohol hybrid matrix was prepared by a sol-gel technique and its capacity to bind porcine pancreatic lipase investigated. The loading of 250 units g −1 support was shown to be effective, resulting in an immobilized lipase with high catalytic activity. Both free and immobilized lipases were characterized by determining the activity profile as a function of pH, temperature, substrate concentration and thermal stability. Application of the immobilized lipase in non-conventional biocatalysis for the synthesis of surfactants and biodiesel was also analyzed. Production of sugar fatty acid esters was found to be dependent on the carbohydrate and the highest molar conversion (50% in 3-4 h of reaction) was achieved for substrates containing fructose and lauric or oleic acids. Biodiesel synthesis from babassu oil and ethanol, propanol or butanol was feasible and regardless of the kind of alcohols, results revealed that the immobilized PPL could efficiently convert triglycerides to fatty acid alkyl esters attaining yields varying from 75 to 95%.

a. Sara Mesquita, 2270, 60511-110 Fortaleza -CE, Brasil Recebido em 16/10/06; aceito em 25/5/07; publicado na web em 9/11/07 COMPARATIVE PERFORMANCE OF Candida rugosa LIPASE IMMOBILIZED ON POLYSILOXANE POLYVINYL ALCOHOL HYBRID SUPPORT USING DIFFERENT METHODOLOGIES. The efficiency for immobilizing microbial Candida rugosa lipase on a hybrid matrix of polysiloxane polyvinyl alcohol, by adsorption, covalent coupling and encapsulation was compared. The activities of immobilized derivatives were evaluated using p-nitrophenylpalmitate (hydrolysis) and butyric acid and butanol (esterification) as substrates. Operational stability and storage tests were also performed. Among the procedures tested, the proposed matrix was efficient for immobilizing C. rugosa lipase by adsorption and covalent coupling techniques and unsuitable for encapsulation purposes. The results reveal that better catalytic properties in both aqueous and organic media were demonstrated by the covalent coupling POS-PVA immobilized lipase, including also satisfactory half-life and good storage stability.Keywords: lipase; hybrid support; adsorption. INTRODUÇÃOEnzimas na sua forma nativa (enzimas livres) têm sido usadas por séculos na indústria de alimentos e mais recentemente nas indústrias farmacêuticas e químicas 1 . Sua estrutura e modo de ação vêm sendo gradativamente elucidados por métodos experimentais bem estabelecidos, como técnicas clássicas de Raio-X e avançadas de Ressonância Nuclear Magnética (RNM). Modernas metodologias de engenharia genética têm possibilitado a produção de enzimas em larga escala ou a modificação de sua estrutura primária, alterando, portanto, algumas de suas características físico-químicas e biológicas 2 . De igual significância são as recentes técnicas de evolução direcionada, as quais têm permitido, via modificação do DNA, a preparação de enzimas especialmente dirigidas para uma determinada finalidade, isto é, enzimas que atuam em valores extremos de pH e temperatura, bem como em presença de meios não convencionais (solventes orgânicos, fase gasosa e CO 2 supercrítico) 3 .O valor de venda de enzimas para uso em indústrias de alimentos, detergentes, especialidades químicas perfizeram um total de aproximadamente US$ 700 milhões em 1992 e aumentaram para US$ 2 bilhões em 2004 4 . De acordo com as projeções, o crescimento no mercado de enzimas é de aproximadamente 4-5% ao ano, acompanhada pela redução de preço, devido ao grande núme-ro de empresas que vêm comercializando enzimas com preços mais competitivos. Como resultado, o mercado previsto para 2009 é da ordem de 2,4 bilhões 4 .De interesse particular é o aumento do uso de enzimas imobilizadas, termo empregado por Katchalski-Katzir 5 na primeira Conferência de Engenharia Enzimática realizada em Henniker, NH, EUA em 1971, para designar enzima fisicamente confinada ou localizada numa certa região do espaço, com retenção de sua atividade catalítica, podendo ser usada repetida e continuamente 6 . Nesta técnica, a enzima fica retida no interior (poros) ou na superfície de u...

Structured lipids (SL) are chemically or enzymatically modified oils and fats with respect to their original fatty acid composition or position in acylglycerols. These compounds present improved functional or nutraceutical properties. The present work aimed at the enzymatic synthesis of SL, MLM-type dietary triacylglycerols, that is, those with medium chain fatty acids (M) at the sn-1 and sn-3 positions, and long chain fatty acids (L), in the internal position of the triacylglycerol. Grapeseed oil was selected based on its composition rich in unsaturated fatty acids, principally linoleic acid. This oil was submitted to batch acidolysis with medium chain fatty acids (caprylic or capric) in solvent-free media. Reactions were catalyzed by different immobilized commercial lipases, namely: Lipozyme TL IM ® (Thermomyces lanuginosa lipase), Lipozyme RM IM ® (Rhizomucor miehei lipase) and Novozym 435 ® (Candida antarctica lipase B). The incorporation degree (ID) ranged from 23.62 ± 1.34 to 34.53 ± 0.05 mol%, after 24 h reaction at 45°C, using a molar ratio (MR) fatty acid:oil of 2:1. The best results were obtained using capric acid and Lipozyme RM IM ® lipase (34.53 ± 0.05 mol%). In the experimental design, the influence of MR and temperature on ID were evaluated. ID increased with MR and T and was fitted to a saddle-like surface.

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