Microbial Nanobiotechnology in Nanocatalysis: Degradation …
387
2.3 Degradation of Chlorinated Aromatic Compounds
The usage of chlorinated aromatic compounds at different levels in industries has
increased vastly owing to their resistance to oxidation, flame resistance, and low
water solubility. This exaggerated use has a principal role in water, air, and soil
pollution. These compounds are quite difficult to remove, and while various redox
approaches have been employed to degrade their firm structure, it is imperative to
devise an effortless yet effective treatment for the dehalogenation of these xenobiotics. Biosynthesized Pd-based nanoparticles have shown incredible results in this
regard. In a study aimed to synthesize Pd nanoparticles, cell surfaces of Desulfovibrio
vulgaris, Desulfovibrio desulfuricans and Desulfovibrio sp. ‘Oz-7’ were used, where
hydrogen acted as electron donor. The bacteria species was proved to affect both the
dehalogenation activities of Pd nanoparticles along with bioreductivity of Pd
2+ . In
comparison with chemical Pd nanoparticles, biogenic Pd nanoparticles have been
found to have a specific rate of dechlorination 30 times higher. This dissimilarity in
catalytic efficiency was ascribed to chemical composition, 3-D array, and functional
group structures (Baxter-Plant et al. 2003).
Pd-NPs were biosynthesized, by another group, using Desulfovibrio desulfuricans and hydrogen as an electron donor. In this study, the resulting chloride release
was used to indicate dehalogenation. The breakdown of 2-chlorophenol biphenyls
and polychlorinated biphenyls was used for the approximation of dehalogenation.
2,3,4,5-tetrachloro biphenyl was dehalogenized, and biosynthesized Pd-NPs were
used to gage the dehalogenation impact in comparison with the chemically reduced
control. The chemically reduced Pd nanoparticles had a chloride release rate of 5%
in comparison with the biosynthesized Pd nanoparticles (Baxter-Plant et al. 2004).
Shewanella oneidensis MR-1 has been used to synthesize Pd nanoparticles. In
the study, nanoparticles were produced both intracellularly and extracellularly. The
electron donors used in this experimentation were H2, lactate, ethanol, pyruvate, and
formate. In both solid and liquid conditions, the resultant Pd nanoparticles demonstrated exceptional dehalogenation of polychlorinated biphenyl congeners. Catalytically, the results produced by just 50 mg/L of biosynthesized Pd nanoparticles gave
results as good as 500 mg/L of chemical Pd nanoparticle powder (Windt et al. 2005).
Microbial reduction of soluble Pd(II) via cells of Shewanella oneidensis MR-1
and of an auto aggregating mutant led to precipitation of palladium Pd(0) nanoparticles inside the periplasmic space (bioPd) and on the cell wall. There were recoveries
with a percentage higher than 90% of Pd associated to biomass due to biosorption
and following bioreduction of Pd(II) with H2, lactate, formate, pyruvate, or ethanol
as electron donors. Therefore, the bioPd(0) nanoparticles produced can reductively
dehalogenate polychlorinated biphenyl congeners in sediment and aqueous matrices.
In assays with concentrations up to 1000 mg Pd(II) l
−1 with depletion of soluble
Pd(II) of 77.4% and higher, bioreduction was observed. Researchers found that
there was more than 90% reduction of PCB 21 (2,3,4-chloro biphenyl) coupled
to production of its dechlorination products PCB 1 (2-chloro biphenyl) and PCB 5
387
2.3 Degradation of Chlorinated Aromatic Compounds
The usage of chlorinated aromatic compounds at different levels in industries has
increased vastly owing to their resistance to oxidation, flame resistance, and low
water solubility. This exaggerated use has a principal role in water, air, and soil
pollution. These compounds are quite difficult to remove, and while various redox
approaches have been employed to degrade their firm structure, it is imperative to
devise an effortless yet effective treatment for the dehalogenation of these xenobiotics. Biosynthesized Pd-based nanoparticles have shown incredible results in this
regard. In a study aimed to synthesize Pd nanoparticles, cell surfaces of Desulfovibrio
vulgaris, Desulfovibrio desulfuricans and Desulfovibrio sp. ‘Oz-7’ were used, where
hydrogen acted as electron donor. The bacteria species was proved to affect both the
dehalogenation activities of Pd nanoparticles along with bioreductivity of Pd
2+ . In
comparison with chemical Pd nanoparticles, biogenic Pd nanoparticles have been
found to have a specific rate of dechlorination 30 times higher. This dissimilarity in
catalytic efficiency was ascribed to chemical composition, 3-D array, and functional
group structures (Baxter-Plant et al. 2003).
Pd-NPs were biosynthesized, by another group, using Desulfovibrio desulfuricans and hydrogen as an electron donor. In this study, the resulting chloride release
was used to indicate dehalogenation. The breakdown of 2-chlorophenol biphenyls
and polychlorinated biphenyls was used for the approximation of dehalogenation.
2,3,4,5-tetrachloro biphenyl was dehalogenized, and biosynthesized Pd-NPs were
used to gage the dehalogenation impact in comparison with the chemically reduced
control. The chemically reduced Pd nanoparticles had a chloride release rate of 5%
in comparison with the biosynthesized Pd nanoparticles (Baxter-Plant et al. 2004).
Shewanella oneidensis MR-1 has been used to synthesize Pd nanoparticles. In
the study, nanoparticles were produced both intracellularly and extracellularly. The
electron donors used in this experimentation were H2, lactate, ethanol, pyruvate, and
formate. In both solid and liquid conditions, the resultant Pd nanoparticles demonstrated exceptional dehalogenation of polychlorinated biphenyl congeners. Catalytically, the results produced by just 50 mg/L of biosynthesized Pd nanoparticles gave
results as good as 500 mg/L of chemical Pd nanoparticle powder (Windt et al. 2005).
Microbial reduction of soluble Pd(II) via cells of Shewanella oneidensis MR-1
and of an auto aggregating mutant led to precipitation of palladium Pd(0) nanoparticles inside the periplasmic space (bioPd) and on the cell wall. There were recoveries
with a percentage higher than 90% of Pd associated to biomass due to biosorption
and following bioreduction of Pd(II) with H2, lactate, formate, pyruvate, or ethanol
as electron donors. Therefore, the bioPd(0) nanoparticles produced can reductively
dehalogenate polychlorinated biphenyl congeners in sediment and aqueous matrices.
In assays with concentrations up to 1000 mg Pd(II) l
−1 with depletion of soluble
Pd(II) of 77.4% and higher, bioreduction was observed. Researchers found that
there was more than 90% reduction of PCB 21 (2,3,4-chloro biphenyl) coupled
to production of its dechlorination products PCB 1 (2-chloro biphenyl) and PCB 5