Improvement of catalytic activity and stability of lipase by immobilization on organobentonite

Organobentonites were prepared from Na-bentonite (NB) by intercalation with cetyltrimethyl ammonium bromide (CTMAB), and used to support the lipase from porcine pancreas. The immobilized lipase showed higher activity in hydrolysis of olive oil than free lipase, with the highest specific activity of 347.8 U g(-1) protein for lipase immobilized on bentonite-CTMAB(100) (BC100-lipase). The apparent activation energy (E-a) of catalysis declined from 29.25 kJ mol(-1) for free lipase to 16.31 kJ mol(-1) for BC100-lipase, resulting in a higher catalytic efficiency of lipase. The improvement of catalytic activity was attributed to the interfacial activation by hydrophobic microenvironment and highly scattered surface created by organobentonite, according to the structural and morphological characterizations by Fourier transform infrared spectroscopy (FTIR) and Transmission electron microscopy (TEM). The immobilized lipase showed better resistance to pH and heating inactivation in comparison to the free lipase. After the storage of 8 days, BC100-lipase retained 80.7% of initial activity, which was 2.7 times higher than the residual activity of free lipase. Particularly, BC100-lipase kept 82.5% of initial activity after 6 continuous recycles under vigorous agitation, showing the excellent stability of the immobilized lipase by adsorption. (C) 2011 Elsevier B.V. All rights reserved.