Hen egg white as a feeder protein for lipase immobilization

Enzyme stabilization via immobilization is one of the preferred processes as it provides the advantages of recovery and reusability. In this study, Thermomyces lanuginosus lipase has been immobilized through crosslinking using 2% glutaraldehyde and hen egg white, as an approach towards CLEA preparation. The immobilization efficiency and the properties of the immobilized enzyme in terms of stability to pH, temperature, and denaturants was studied and compared with the free enzyme. Immobilization efficiency of 56% was achieved with hen egg white. The immobilized enzyme displayed a shift in optimum pH towards the acidic side with an optimum at pH 4.0 whereas the pH optimum for free enzyme was at pH 6.0. The immobilized enzyme was stable at higher temperature retaining about 83% of its maximum activity as compared to the free enzyme retaining only 41% activity at 70 °C. The denaturation of lipase in free form was rapid with a half-life of 2 h at 60 °C and 58 min at 70 °C as compared to 12 h at 60 °C and 2 h at 70 °C for the immobilized enzyme. The effect of denaturants, urea and guanidine hydrochloride on the free and immobilized enzyme was studied and the immobilized enzyme was found to be more stable towards denaturants retaining 74% activity in 8 M urea and 98% in 6 M GndHCl as compared to 42% and 33% respectively in the case of free enzyme. The apparent Km (2.08 mM) and apparent Vmax (0.95 μmol/min) of immobilized enzyme was lower as compared to free enzyme; Km (8.0 mM) and Vmax (2.857 μmol/min). The immobilized enzyme was reused several times for the hydrolysis of olive oil.

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► The use of hen egg white as a feeder protein for the immobilization of Thermomyces lanuginosus lipase.
► Characterization of the immobilized enzyme in terms of various parameters.
► The immobilized enzyme showed an improved stability to heat and denaturants such as urea and guanidine hydrochloride as compared to the free enzyme.
► The immobilized enzyme retained good storage and operational stability.