title: Continuous biodegradation of parathion by immobilized Sphingomonas sp. in magnetically fixed-bed bioreactors and evaluation of the enzyme stability of immobilized bacteria.
abstract: Magnetically-modified Sphingomonas sp. was prepared using covalent binding of magnetic nanoparticles on to the cell surface. The magnetic modified bacteria were immobilized in the fixed-bed bioreactors (FBR) by internal and external magnetic fields for the biodetoxification of a model organophosphate, parathion: 93 % of substrate (50 mg parathion/l) was hydrolyzed at 0.5 ml/min in internal magnetic field fixed-bed bioreactor. The deactivation rate constants (at 1 ml/min) were 0.97 × 10(-3), 1.24 × 10(-3) and 4.17 × 10(-3) h(-1) for immobilized bacteria in external and internal magnetic field fixed-bed bioreactor and FBR, respectively. The deactivation rate constant for immobilized magnetically modified bacteria in external magnetic field fixed-bed bioreactor (EMFFBR) was 77 % lower than that of immobilized cells by entrapping method on porous basalt beads in FBR at 1 ml/min. Immobilized magnetic modified bacteria exhibited maximum enzyme stability in EMFFBR.
authors.affiliation: Department of Biotechnology, Malek-Ashtar University of Technology, Tehran, Islamic Republic of Iran.
authors.forename: Seyed Mortaza
authors.initials: SM
authors.lastname: Robatjazi
authors.forename: Seyed Abbas
authors.initials: SA
authors.lastname: Shojaosadati
authors.forename: Rassoul
authors.initials: R
authors.lastname: Khalilzadeh
authors.forename: Ebrahim Vasheghani
authors.initials: EV
authors.lastname: Farahani
authors.forename: Mehdi
authors.initials: M
authors.lastname: Zeinoddini
mesh_terms: D043303:Aryldialkylphosphatase / Q000737:chemistry / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D001673:Biodegradation, Environmental; D019149:Bioreactors / Q000382:microbiology*; D018914:Cells, Immobilized / Q000201:enzymology* / Q000378:metabolism; D004795:Enzyme Stability; D006868:Hydrolysis; D058185:Magnetite Nanoparticles / Q000737:chemistry*; D010278:Parathion / Q000493:pharmacokinetics*; D020578:Sphingomonas / Q000201:enzymology* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D058185:Magnetite Nanoparticles; D010278:Parathion; D043303:Aryldialkylphosphatase