The study on effective immobilization of lipase on functionalized bentonites and their properties

Three different functionalized bentonites including acid activated bentonite (B-a), organically modified bentonite with cetyltrimethyl ammonium bromide (B-CTMAB) and the composite by acid activation and organo-modification (Ba-CTMAB) were prepared, and used for immobilization of lipase from bovine pancreatic lipase by adsorption. The amount of lipase adsorbed on the functionalized bentonites was in the following sequence: B-a > B-CTMAB > Ba-CTMAB, showing the strongest affinity of B-a for lipase among the three supports. However, the immobilized lipase on Ba-CTMAB showed the highest activity in the hydrolysis of olive oil by 1.67 times of activity of free lipase due to the hydrophobically interfacial activation and enlarged catalytic interface. While, the activity of immobilized lipase on B-a was lower than 20% of free lipase's activity due to the absence of hydrophobic activation and negative impact of excessive hydrogen ions on the surface. The K-m values for the immobilized lipase on Ba-CTMAB (0.054 g/mL) and B-CTMAB (0.074 g/mL) were both lower than that of free lipase (0.115 g/mL), and the V-max values were higher for the immobilized lipases, exhibiting a higher affinity of the immobilized lipase toward olive oil than free lipase. In comparison to free lipase, the better resistance to heating inactivation, storage stability and reusability of the immobilized lipases on Ba-CTMAB and B-CTMAB were also obtained. The results show that the efficient and stable biocatalysts for industrial application can be prepared by using the low-cost bentonite mineral as the supports. (c) 2013 Elsevier B.V. All rights reserved.