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Open Access Research article

Biodegradation of 2,4-dinitrophenol with laccase immobilized on nano-porous silica beads

Emad Dehghanifard1, Ahmad Jonidi Jafari23*, Roshanak Rezaei Kalantary14, Amir Hosein Mahvi13, Mohammad Ali Faramarzi5 and Ali Esrafili1

Author Affiliations

1 Department of Environmental Health Engineering, School of Public Health, Tehran University of Medical Sciences, Tehran, Iran

2 Department of Environmental Health, Faculty of Medical Sciences, Tarbiat Modares University, Tehran, Iran

3 Center for Solid Waste Research (CSWR), Institute for Environmental Research (IER), Tehran University of Medical Sciences, Tehran, Iran

4 Center for Water Quality Research (CWQR), Institute for Environmental Research (IER), Tehran University of Medical Sciences, Tehran, Iran

5 Department of Pharmaceutical Biotechnology, Faculty of Pharmacy, Tehran University of Medical Sciences, Tehran, Iran

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Iranian Journal of Environmental Health Science and Engineering 2013, 10:25  doi:10.1186/1735-2746-10-25

Published: 1 April 2013

Abstract

Many organic hazardous pollutants, including 2,4-dinitrophenol (2,4-DNP), which are water soluble, toxic, and not easily biodegradable make concerns for environmental pollution worldwide. In the present study, degradation of nitrophenols-contained effluents by using laccase immobilized on the nano-porous silica beads was evaluated. 2,4-DNP was selected as the main constituent of industrial effluents containing nitrophenols. The performance of the system was characterized as a function of pH, contact time, temperature, pollutant, and mediator concentrations. The laccase-silica beads were employed in a mixed-batch reactor to determine the degradation efficiency after 12 h of enzyme treatment. The obtained data showed that the immobilized laccase degraded more than 90% of 2,4-DNP within 12 h treatment. The immobilization process improved the activity and sustainability of laccase for degradation of the pollutant. Temperatures more than 50°C reduced the enzyme activity to about 60%. However, pH and the mediator concentration could not affect the enzyme activity. The degradation kinetic was in accordance with a Michaelis–Menten equation with Vmax and Km obtained as 0.25–0.38 μmoles/min and 0.13–0.017 mM, respectively. The stability of the immobilized enzyme was maintained for more than 85% of its initial activity after 30 days. Based on the results, it can be concluded that high resistibility and reusability of immobilized laccase on CPC-silica beads make it considerable choice for wastewater treatment.

Keywords:
Degradation; Laccase; Immobilization; Nano-porous silica beads; 2,4-dinitrophenol