FTIR, SEM and fractal dimension characterization of lipase B from Candida antarctica immobilized onto titania at selected conditions

Abstract

Lipase B from Candida Antarctica (also known as Candida antarctica lipase B or CALB) was immobilized onto titanium dioxide (TiO2) in a buffer-free, bidistilled aqueous medium. The adsorption isotherm was determined by UV–vis analysis of supernatant solution at 280 nm, revealing that in 7 h 98% of the theoretical lipase monolayer on the TiO2 (with 45.7 m2 /g BET area) was achieved. Samples withdrawn from the supernatant immobilization medium were analyzed by Fouriertransform infrared spectroscopy in the 1700–1600 cm1 range (where the Amide I Proteins band appears) in order to obtain quantitative information on the evolution of the secondary-structure elements of the protein. The analysis performed revealed that lipase conformation suffers only minor changes during its adsorption onto TiO2. However, water associated to the lipase may interact of several ways with the surface of the hydrated oxide. Characterization of the immobilized biocatalyst (CALB/TiO2) implied SEM, fractal dimension analysis and FTIR techniques. A proposal of lipase-hydrated oxide interaction is presented.