Bacterial Enzymes and Their Role in Decolorization of Azo Dyes - Microbial Degradation of Synthetic Dyes in Wastewaters - page 157

Methyl Orange

Asymmetric Cleavage by
Purified Laccase

p - phenyldiazine sulphonic acid p -hydroxy N,N'dimethyl benzene

Fig. 11 Proposed degradation pathway for Methyl Orange by puri ed laccase

7.3 Lignin Peroxidase Mediated Dye Decolorization

The lignin peroxidase puri ed from Bacillus laterosporus was decolorizes Methyl

Orange (Gomare et al. 2008 ). The biodegradation pathway of Methyl Orange was
shown in Fig. 12 .
In degradation pathway, Methyl Orange rstly forms cyclo-2, 5-ene-1-one rad-

icals with the removal of sulfate ion, N, N di methylamine and a nitrogen molecule,
where these two radicals condense to produce 1, 1 ′ -dicyclohex-2, 5-ene-4-one
moiety. Its one of the cyclohexene rings undergoes -cleavage to form 4-substituted

hexanoic acid, which on the removal of methyl radical undergoes cyclization to
produce 4-cyclohexenone lactone cation. This substituted lactone cation

α

nally
forms a stable molecule of p-isopropanal-2,5-cyclohexa-dienone with the elimina-
tion of iminium moiety (Gomare et al. 2008 ).

7.4 Veratrol Alcohol Oxidase Mediated Dye Decolorization

The veratrole alcohol oxidase was puri ed from Comomonas sp. UVS and assessed

fordye decolorization (Jadhav et al. 2009 ). Oxidative cleavage of Red HE7B
(RRHE7B) yielded an unknown product. This product further undergoes desulfo-
nation to give naphthalene-1,2,5-triol (Fig. 13 ). The use of puri

ed enzyme sug-

gested their direct involvement for dye decolorization.

8 Toxicity of Azo Dyes and Its Degradation Metabolites

The wastewater released from the textile industries after the treatment is sometime
used for irrigation purpose in the agricultural

elds (Paul et al. 2012 ). Hence, the
toxicity assessment for the seed germination and plant growth of treated textile