Biocatalytic characterization of a naturally immobilized lipase found in Araujia sericifera Brot. (Apocynaceae) latex

Abstract

Lipase activity found in the insoluble fraction of Araujia sericifera Brot. (Apocynaceae) (ASL) latex, a native South American milkweed, was characterized by use of different test reactions and under different reaction conditions. In this context, hydrolytic lipase activity towards both natural and synthetic substrates and towards fatty acid esterifications was assayed at different temperatures, pH values, and biocatalyst loads. In the case of natural substrates (cottonseed oil), highest lipase activity was found at pH 8.5 and 60 °C. In the hydrolysis of synthetic substrates (p-nitrophenyl esters) the lipase showed preference for the lowest molecular-weight p-nitrophenyl ester assayed (butyrate). Results of the direct esterification of fatty acids of different chain length in organic media showed that esterification levels of up to 45% could be obtained in one hour of reaction. Activity results were compared with the activity shown by the commercial immobilized lipase Novozym 435 under defined reaction conditions. The high activity exhibited by ASL in the hydrolysis of natural substrates and particularly in the direct esterification of different fatty acids in organic medium, together with its high storage stability, suggests that this plant lipase is a promising biocatalyst for various biotechnological applications.