title: Activity stabilization of Aspergillus niger and Escherichia coli phytases immobilized on allophanic synthetic compounds and montmorillonite nanoclays.
abstract: The aim of this work was to study the stabilization of the activity of two commercial microbial phytases (Aspergillus niger and Escherichia coli) after immobilization on nanoclays and to establish optimal conditions for their immobilization. Synthetic allophane, synthetic iron-coated allophanes and natural montmorillonite were chosen as solid supports for phytase immobilization. Phytase immobilization patterns at different pH values were strongly dependent on both enzyme and support characteristics. After immobilization, the residual activity of both phytases was higher under acidic conditions. Immobilization of phytases increased their thermal stability and improved resistance to proteolysis, particularly on iron-coated allophane (6% iron oxide), which showed activation energy (E(a)) and activation enthalpy (ΔH(#)) similar to free enzymes. Montmorillonite as well as allophanic synthetic compounds resulted in a good support for immobilization of E. coli phytase, but caused a severe reduction of A. niger phytase activity.
authors.affiliation: Chile-Italy International Doctorate in Environmental Resources Science, Universidad de La Frontera, Temuco, Chile, and Università di Napoli Federico II, Portici, Italy.
authors.forename: Daniel
authors.initials: D
authors.lastname: Menezes-Blackburn
authors.forename: Milko
authors.initials: M
authors.lastname: Jorquera
authors.forename: Liliana
authors.initials: L
authors.lastname: Gianfreda
authors.forename: Maria
authors.initials: M
authors.lastname: Rao
authors.forename: Ralf
authors.initials: R
authors.lastname: Greiner
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Garrido
authors.forename: María
authors.initials: M
authors.lastname: de la Luz Mora
mesh_terms: D010832:6-Phytase / Q000378:metabolism*; D000538:Aluminum Silicates; D001234:Aspergillus niger / Q000201:enzymology*; D001546:Bentonite; D000077215:Clay; D004800:Enzymes, Immobilized / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology*; D036103:Nanotechnology; D059748:Proteolysis; D013696:Temperature; D013816:Thermodynamics; D014961:X-Ray Diffraction
chemical_list: D000538:Aluminum Silicates; D004800:Enzymes, Immobilized; D001546:Bentonite; D010832:6-Phytase; D000077215:Clay