Bacterial Degradation of Textile Dyes - Microbial Degradation of Synthetic Dyes in Wastewaters - page 249

them are known to be carcinogenic. The emphasis is currently on the reduction of
trace metals in textile processing ef uent. It has been suggested that the heavy

metals present in the dye bath would not affect the performance of bacteria during
the degradation of the organic matters in the biochemical process (Boopathy 2000 ;
Uddin et al. 2007 ).

4 Involvement of Oxidoreductive Enzymes in Degradation
Process

In recent years, the enzymatic approach has attracted much interest in the bio-
degradation and decolorization of textile and other industrial wastewater. Enzy-
matic treatment is usually very effective in the degradation of pollutants. The
potential of the enzymes like cytochrome P450, manganese peroxidases, lignin
peroxidases, laccases, polyphenol oxidases, and azoreductases, has been studied in
the decolorization and degradation of dyes. The expression of the enzymes
involved in dye degradation may vary with time, but dependent on the growth
phase of the microorganisms, and is also in uenced by other compounds present in

the ef uent. There is an increasing industrial value for the alternative cost effective

method for treatment of a large volume of wastewater. The application of enzyme-
based systems in waste water treatment is highly valuable (Husain 2006 ).

4.1 Cytochrome P450

Cytochrome P450 (CYP) represents one of the largest and oldest gene super
families coding for enzymes present in the genomes of all biological kingdoms. The
terminology CYP is uncommon for enzymes, because it is not based on function,
but describes originally the spectral properties of b-type heme containing red pig-
ments, which display a typical absorption band at 450 nm of their reduced carbon-
monoxide bound form (Omura and Sato 1962 ). In mammals, azo dyes are reduced
to aryl amines by CYP and a avin dependent cytosolic reductase. The reactions

catalysed can be extremely diverse as hydroxylations, N

, and S-dealkylations,
sulfoxidations, epoxidations, deaminations, desulfurations, dehalogenations, per-
oxidations, and N-oxide reductions (Bernhardt 2006 ). Since many of the individual
CYP catalyse multiple reactions, the usual method of naming enzymes is inade-
quate for this group of proteins, and a systematic nomenclature has been derived
based on structural homology. The CYP has been exclusively studied for detoxi-

,O

- -

cation and degradation. The degradation of various textile dyes by Alishewanella
sp. KMK6 showed an induction in CYP activities in the cells after dye decolor-
ization indicating the role of these enzymes (Kolekar and Kodam 2012 ). Recently