Bacterial Enzymes and Their Role in Decolorization of Azo Dyes - Microbial Degradation of Synthetic Dyes in Wastewaters - page 159

Cl

H

N N

SO 3 H SO 3 H

OH

OH H N N N

N N N N

N N

N
H

H

SO 3 H

SO 3 H SO 3 H

SO 3 H SO 3 H

RRHE7B
MW= 1480

Oxidative cleavage

Cl

H

N N

SO 3 H

SO 3 H

OH H N N N OH

OH

NH 2 N N N

N N

+

N
H

N
H

SO 3 H

SO 3 H

SO 3 H

SO 3 H

Unknown product

Unknown product

Desulfonation

OH

OH

OH

Naphthalene-1,2,5-triol
MW= 176

Fig. 13 Proposed degradation pathway for RRHE7B by Veratryl alcohol oxidase

azoreductase. Aromatic amines are highly toxic and carcinogenic in nature. On the
other hand, decolorization of azo dyes by fungal species involves the role of oxi-
dases which don

t produce the toxic aromatic amines. Therefore, a consortium of
bacteria and fungus used for decolorization of azo dyesproduces metabolite which
was free from carcinogenic aromatic amines. Metabolites analyzed after decolor-
ization of azo dye disperse Rubine GFL by consortium of Pseudomonas sp. SUK1
and Aspergillus orchaceus NCIM 1146, showed absence of the aromatic amines.
However, Pseudomonas sp. SUK1 showed 0.14 mM concentration of aromatic
amines (Lade et al. 2012 ). At the same time, Aspergillus orchaceus NCIM 1146
showed no presence of the aromatic amines. Therefore, use of enzymatic systems
from fungal-bacterial co-cultures for decolorization of azo dyes enhances detoxi-

'

cation of azo dyes with enhanced biodegradationrate (Lade et al. 2012 ).