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The mixed intracellular enzyme (MICE) from Citrobacter freundii, capable of degrading o-phenylene diamine (OPD), was extracted and characterized. Cofactors such as zinc and copper ions enhanced the MICE activity. The functionalized nanoporous-activated carbon (FNAC) matrix, zinc-impregnated FNAC matrix (Zn2+-FNAC), copper-impregnated FNAC matrix (Cu2+-FNAC), and zinc- and copper-impregnated FNAC matrix (Zn2+-Cu2+-FNAC) were prepared and characterized to immobilize MICE. The parameters such as time (0-240 Min), pH (1-10), temperature (20-50 ºC), amount of MICE (1-5 mg), particle size of carbon (100-600 μm), and mass of carbon (0.5-2.5 g) were optimized for immobilization of MICE on different FNAC matrices. The carrier matrices in the free and MICE immobilized form were characterized using SEM, FT-IR, XPS, XRD, thermogravimetric analysis (TGA), and DSC analyses. The kinetic and adsorption models for the immobilization of MICE on FNAC matrices were studied. The parameters such as time, pH, temperature, concentration of OPD, and agitation speed were optimized for the degradation of OPD using FNAC-MICE and MICE-immobilized metal-impregnated FNAC matrices. The maximum amount of pyruvic acid formed was found to be 133 μg/mg of OPD using Zn2+-Cu2+-FNAC-MICE matrix. The kinetic models were studied for the formation of pyruvic acid on OPD degradation and confirmed using FT-IR spectroscopy. [ABSTRACT FROM AUTHOR]

BACKGROUND: Endocrinedisrupting chemicals arewidely distributed in environment. o-Phenylenediamine (OPD), anendocrine disruptor, is widely used in the leather, dyeing and polymer industries. There have been studies on the photocatalytic and biological degradation of OPD but there is no single report on the enzymatic degradation of OPD. RESULTS: In the present investigation, purified mixed intracellular enzymes (MIE) were used for the degradation of aqueous OPD fromCitrobacter freundii, a marine bacterium. The degradation rate of OPD (concentration, 333 ppm) by MIE was achieved with maximum removal of 93%. The degrading efficiency using MIE was enhanced by Zn2+ to about 95.87%. The degradation of OPD using MIE of C. freundii followed pseudo-second-order rate kinetics. Fourier transform infrared spectroscopy, ultraviolet-visible spectroscopy, fluorescence spectroscopy, high-performance liquid chromatography and cyclic voltammetry were used to characterise the degradation of OPD by enzymatic treatment. Nuclear magnetic resonance spectroscopy and gas chromatography-mass spectrometry were used for confirmation of the end product of OPD in enzymatic treatment. CONCLUSION: The endocrine disruptor OPD was degraded into pyruvic acid, a non-toxic end product, using MIE. [ABSTRACT FROM AUTHOR]