Environmental Engineering Reference
In-Depth Information
reductively and utilize amines as the source of carbon and energy for their growth.
Such organisms are speci
c to their substrate. Examples of bacterial strains with this
trait are Xenophilus azovorans KF46 (previously Pseudomonas sp. KF46) and
Pigmentiphaga kullae K24 (previously Pseudomonas sp. K24), which can grow
aerobically on Carboxy Orange I and Carboxy Orange II, respectively (McMullan
et al. 2001 ). Only a few bacteria with specialized azo dye reducing enzymes have
been found to degrade azo dyes under fully aerobic conditions (Saratale et al. 2011 ;
Solis et al. 2012 ).
7 Analytical Methods for Evaluation of Dye Degradation
Mechanism
Various analytical techniques are used to identify the intermediates and end metab-
olites generated during azo dye decolorization by bacteria. Amongst all, UV-Vis
spectroscopy is preliminary method used by all researchers to evaluate dye decol-
orization. In this method, dye sample gives a sharp peak at
λ max in visible region,
while after bacterial treatment decolorized sample shows a decrease in intensity
or complete disappearance of the peak with simultaneous increase in intensity of
peaks in the UV region. For further evaluation of metabolite generation and dye
degradation, Thin Layer Chromatography (TLC) and High Performance Thin Layer
Chromatography (HPTLC) techniques are used which gives insights in numbers and
types of metabolites generated. But for con
rmation of the degradation of dye, HPLC
has been used by many investigators, which show appearance of new HPLC peaks
having different retention time (R t ) as compared to HPLC peaks of original dye
chromatogram. Moreover, Fourier Transform Infrared Spectroscopy (FTIR) is widely
used to determine the type and strength of interactions that occur within azo dyes
containing different functional groups after treatment by bacteria. FTIR is compar-
atively more important to check the removal of azo group from the azo dye and
generation of new type of metabolites. Another powerful techniques used for eval-
uation of metabolites are Gas Chromatography-Mass Spectrometry (GC-MS) and
Liquid Chromatography-Mass Spectrometry (LC-MS). Both these techniques are
used for qualitative determination of metabolites along with molecular weights and
their structural information. This information of metabolites is used further to propose
the degradation pathway of the dye. Now-a-days, apart from these techniques,
advance and very complex technique like Nuclear Magnetic Resonance (NMR) is
applied for further detailed quantitative study of compounds and also to get structural
information concerning molecular compounds. But for dye containing wastewater
degradation analysis, these techniques are not very bene
cial, because composition of
actual wastewater is unknown and also complex. So, analysis and interpretation
by these methods are not much helpful as in case of pure dye degradation by bacteria.
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