Make proper surfaces for immobilization of enzymes: Immobilization of lipase and a-amylase on modified Na-sepiolite
Shiva Mortazavi, Hamidreza Aghaei
Department of Chemistry, Shahreza Branch, Islamic Azad University, P.O. Box 311-86145, Shahreza, Isfahan, Iran.
This paper has focused on making suitable carriers for the immobilization of α-amylase from Bacillus subtilis and lipase from Candida rugosa via adsorption on modified Na-sepiolite (SEP). Two modified carriers were prepared by changing the nature of SEP with cetrimonium bromide surfactant at concentrations below the CMC of the surfactant, to produce SEP with monolayer surfactant (MSEP) with hydrophobic properties and above the CMC of the surfactant to produce SEP with bilayer surfactant (BSEP) with hydrophilic properties. The enzymatic activity of immobilized lipase on MSEP (MSEPL) and immobilized α-amylase on BSEP (BSEPA) was successfully tested in the hydrolysis of olive oil and starch. The support modification and immobilization process were characterized by BET, XRD, and SEM techniques. The results demonstrated that the specific activity of MSEPL and BSEPA was 1.74 and 2.28 U/mg, respectively. The remained activity of MSEPL (56.7%) and BSEPA (40.4%) after their incubation at 60 °C for 4 h was much higher than that of free enzymes. The residual activity of MSEPL and BSEPA was 77.4% and 66.7%, after 30 days of storage at 4 °C. The MSEPL and BSEPA also showed good reusability, and their relative activities were 54.0% and 44.2% after ten cycles.
Keywords: Enzyme immobilization, Na-sepiolite, Support modification.