title: Production of partially phosphorylated myo-inositol phosphates using phytases immobilised on magnetic nanoparticles.
abstract: Phytases of different origin were covalently bound onto Fe3O4 magnetic nanoparticles (12 nm). Binding efficiencies of all three phytases were well above 70% relative to the number of aldehyde groups available on the surface of the magnetic nanoparticles. Temperature stability for all three phytases was enhanced as a consequence of immobilisation, whereas pH dependence of enzyme activity was not affected. Maximum catalytic activity of the immobilised phytases was found at 60°C (rye), 65°C (Aspergillus niger) and 70°C (Escherichia albertii). The immobilised enzymes exhibited the same excellent substrate specificities and unique myo-inositol phosphate phosphatase activities as their soluble counterparts. However, the catalytic turnover number dropped drastically for the immobilised phytases. The amount of the desired partially phosphorylated myo-inositol phosphate isomer could be easily controlled by the contact time of substrate solution and immobilised enzymes. The immobilised phytases showed a high operational stability by retaining almost full activity even after fifty uses.
authors.affiliation: Max Rubner-Institut, Department of Food Technology and Bioprocess Engineering, Haid-und-Neu-Strasse 9, 76131 Karlsruhe, Germany. ralf.greiner@mri.bund.de
authors.forename: Ralf
authors.initials: R
authors.lastname: Greiner
authors.forename: Ursula
authors.initials: U
authors.lastname: Konietzny
authors.forename: Daniel Menezes
authors.initials: DM
authors.lastname: Blackburn
authors.forename: Milko A
authors.initials: MA
authors.lastname: Jorquera
mesh_terms: D010832:6-Phytase / Q000378:metabolism*; D004800:Enzymes, Immobilized / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D006868:Hydrolysis; D007295:Inositol Phosphates / Q000378:metabolism*; D007700:Kinetics; D008280:Magnetics; D053758:Nanoparticles; D010766:Phosphorylation; D013379:Substrate Specificity; D013696:Temperature
chemical_list: D004800:Enzymes, Immobilized; D007295:Inositol Phosphates; D010832:6-Phytase
keywords: Immobilisation; Magnetic nanoparticles; Phytase; Phytate; myo-inositol phosphates