Desenvolvimento de sistemas enzimÃticos (lipases) para aplicaÃÃo na hidrÃlise e sÃntese de Ãsteres

AUTOR(ES)
DATA DE PUBLICAÇÃO

2003

RESUMO

A commercial lipase from Mucor miehei was immobilized onto different supports, nylon, nylon-polyvinyl alcohol (nylon-PVA) and polysiloxane-polyvinyl alcohol magnetic particles (POS-PVA), and were tested for hydrolytic activity. Lipase-POS/PVA was the immobilized system with higher operational stability, so their apparent Km and Vmax, optimum temperature and optimum pH were determined, employing r-nitrofenilpalmitate as substrate. Lipase-POS-PVA exhibited Km and Vmax values of 228.3mM and 36.06mmol.min-1 per miligram of protein, respectively, at 30oC and pH 8.0. Optimum temperature and pH were 45oC and pH = 8.0, respectively. The immobilized system was able to perform seven hydrolysis assays, with a residual activity of 69.1% after immobilization. Ester synthesis catalyzed by lipase-POS-PVA was also investigated. The effects of organic acid/alcohol molar ratio, enzyme concentration, carbon chain length of the reactants and the alcohol structure were determined on the reaction rate. Ester synthesis was maximized for substrates containing organic acid in excess and biocatalyst concentration of 25mg/mL. The biocatalyst selectivity for the carbon chain length was found to be different concerning the organic acids and alcohols. The highest reaction rates were achieved for organic acids with 8 or 10 carbons, while the increasing of the length of the alcohol carbon chain from 4 to 8 carbons reduced the esterification yields. Optimal reaction rate was determined for the synthesis of butyl caprylate (12 carbons). The rate of synthesis was also dependent on the alcohol structure, with maximum activity occurring for primary alcohol

ASSUNTO(S)

imobilizaÃÃo sol-gel ciencias biologicas mucor miehei sol-gel lipase mucor miehei immobilization nylon esterificaÃÃo nylon lipase esterification

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