Bacterial Degradation of Azo Dye Containing Wastes - Microbial Degradation of Synthetic Dyes in Wastewaters - page 58

2.1 Bacterial Degradation of Azo Dyes by Pure Culture

Attempts to isolate pure bacterial cultures capable of degrading azo dyes started way
back in 1970s with isolation of Bacillus subtilis, Aeromonas hydrophila and Bacillus
cereus (Wuhrmann et al. 1980 ). Application of single bacterial cultures like Proteus
mirabilis, Pseudomonas luteola, and Pseudomonas sp., has shown very promising
results for the azo dye degradation under anoxic conditions (Saratale et al. 2011 ).
Besides, there are other several studies describing the decolorization of reactive azo
dyes mediated by pure bacterial culture which have been summarized in Table 2 .
Apart from them, other bacterial strains of Desulfovibrio desulfuricans, Exiguo-
bacterium sp., Sphingomonas sp., Rhizobium radiobacter and Comamonassp. were
also reported for decolorization of various azo dyes. Among these strains, Pseu-
domonas is widely used for decolorization study of azo dyes and also exploited
widely to decolorize commercial textile azo dyes, such as Red BLI, Reactive Red 2,
Red HE7B, Reactive Blue 172, Reactive Red 22, Orange I and II. Azo dyes are
generally resistant to bacterial attack under aerobic conditions due to inhibition of
azo reductase activity in presence of oxygen. However, a few selected aerobic
bacterial strains possess the ability to reduce azo linkage by oxygen insensitive or
aerobic azoreductases. A. hydrophila was studied for azo dye decolorization under
aerobic conditions by Chen et al. ( 2009 ). Micrococcus sp. is an interesting example
which decolorizes dyes faster under aerobic conditions than in anaerobic environ-
ments. In an oxygen free atmosphere (N 2 atmosphere), no decolorization was
observed by B. lentus, indicating that culture required certain amount of O 2 for the
decolorization process. Use of a pure culture system ensures reproducible data, and
also becomes easier for interpretation of experimental observations. Such studies

Table 2 Examples of degradation study of azo dyes by pure bacterial culture
Bacterial culture Azo dyes References

Pseudomonas spp. Red BLI Kalyani et al. ( 2008a )

Reactive Red BS Sheth and Dave ( 2009 )

Reactive Red 2 Kalyani et al. ( 2008b )

Red HE7B Kalme et al. ( 2007 )

Reactive Blue 172 Bhatt et al. ( 2005 )

Reactive Red 22 Hu ( 2001 ), Chang

and Lin ( 2000 )

Orange I and II Kulla et al. ( 1983 )

Proteus spp. Red RBN Chen et al. ( 1999 )

Shewanella spp. Acid Red GR Xu et al. ( 2007 )

Remazol Black B and Anthraquinone dye Bragger et al. ( 1997 )

Bacillus spp. Acid Red 119 Dave and Dave ( 2009 )

Disperse Blue 79 and Acid Orange 10 Kolekar et al. ( 2008 )

Navy Blue 2GL Dawkar et al. ( 2009 )