Monday, April 30, 2012
Napoleon Ballroom C-D, 3rd fl (Sheraton New Orleans)
Lipases (triacyl-glycerol-hydrolases) are enzymes that catalyze hydrolysis, esterification and interesterification reactions. Although they can be obtained from animals, microbial and vegetable sources, nowadays commercial lipases are widely supplied by fungi or bacteria. The high cost of those biocatalysts is a drawback for their use in some industrial applications. In this work, oilseeds (sunflower and soy seeds) were investigated as sources of lipases for producing low-cost immobilized biocatalysts. Immobilized lipases can provide non-aqueous conditions necessary for ester synthesis and interesterification reactions. The oilseeds were triturated in 50mM sodium phosphate buffer, pH 7.0, followed by agitation by 11h at 25oC. The solids were separated by filtration and the crude extract was clarified by centrifugation and partially purified by ultrafiltration in a 100 kDa cut-off membrane. Partial purified lipases were dialyzed and immobilized on hydrophobic silica (octyl-silica) at 25oC, pH 7.0 and low ionic strength. After the extraction step, lipase specific activities were ca. 81 and 100 IU/gseeds (dry basis) for sunflower and soy seeds, respectively. After ultrafiltration, the recovered total activities were 46.3% and 43.5%. Despite these values, the enzymatic solutions had specific activities ca. 47 and 43 times higher than the crude extracts. The immobilization yield was ca. 90% for both oilseed lipases. Remarkably, the immobilized lipases were 4 to 7 times more actives than the soluble ones. This behavior is probably due to an interfacial activation of the lipases on the hydrophobic surface. These results show that immobilized lipases from oilseeds are potential sources of low-cost biocatalysts for organic-synthesis applications.