Continuous biodegradation of parathion by immobilized Sphingomonas sp. in magnetically fixed-bed bioreactors and evaluation of the enzyme stability of immobilized bacteria |
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Authors: | Seyed Mortaza Robatjazi Seyed Abbas Shojaosadati Rassoul Khalilzadeh Ebrahim Vasheghani Farahani Mehdi Zeinoddini |
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Institution: | 1. Department of Biotechnology, Malek-Ashtar University of Technology, Tehran, Islamic Republic of Iran 2. Biotechnology Group, Faculty of Chemical Engineering, Tarbiat Modares University, 14115-114, Tehran, Islamic Republic of Iran
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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. |
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