The Biodegradation of Azo Dyes by Actinobacteria - Microbial Degradation of Synthetic Dyes in Wastewaters - page 297

degradation of dye chemicals. Usually, the dye degradation occurs by the activity of
lignin peroxidase, laccase, NADH-DCIP reductase or azoreductase enzymes
(Sahasrabudhe and Pathade 2013 ).
Actinomycetes show a variable potential to degrade various synthetic dyes.
Chengalroyen ( 2011 ) examined the decolorization behaviour of Streptomyces
species against two structurally different dyes (Congo red and Orange II). Strep-
tomyces species were able to decolorize structurally complex dye Congo red with
two azo bonds and poly aromatic and sulfonated groups, while structurally simpler
dye Orange II (with a single azo bond and sulfonated group) was not decomposed.
Biodegradation of triphenyl methane dyes by two actinomycetes, such as Nocardia
corallina and Nocardia globerula, was reported by Yatome et al. ( 1991 ).The
Crystal Violet dye was completely decolorized within 24 h. Nocardia coralline was
also able to decolorize four triphenyl methane dyes, such as Methyl Violet, Ethyl
Violet, Basic Fuchsin and Victoria Blue, but maximum decolorization was
observed in Crystal Violet dye. They suggest that the decolorization activity of
actinomycetes is intracellular, as there was no activity in the culture ltrate. Sim-

ilarly, the decolorization activity was not observed in washed cells of N. corallina,
when the cells were incubated in a buffer, but the activity was recovered when the
cells were incubated in LB medium. Bhaskara et al. ( 2003 ) reported that extra-
cellular

uid protein (ECFP) of Streptomyces species could be used for the
reduction of azo dyes soluble in water.
Sahasrabudhe and Pathade ( 2013 ), in a study, indicated that Georgenia sp.
CC-NMPT-T3 could degrade the individual as well as mixture of ve different dyes

under static anoxic conditions (Sahasrabudhe and Pathade 2013 ). This suggests its
potential to be used as inoculum in the bioreactor for the treatment of textile
wastewater containing a variety of synthetic dyes. Under shaking condition,
Streptomyces krainskii strain SUK -5 completely degraded textile dye Reactive
blue-59 within 24 h (Mane et al. 2008 ). During the process of degradation of
Reactive blue-59, the involvement of lignin peroxidase, and NADH-DCIP reduc-
tase and MR reductase enzymes was con rmed.

Consortium of different actinomycetes can also be used for the degradation of
azo dyes. Bagewadi et al. ( 2011 ) developed a consortium having

ve actinomycetes
strains. About 97.44 % of degradation of reactive yellow dye (5 mg 100 ml − 1 ) was
observed by this consortium in 15 days. They concluded that degradation of the dye
depends on the concentration of dye, as well as on the growth of actinomycetes.
El-Sersy et al. ( 2011 ) studied the potential of

ve actinomycetes (Streptomyces
globosus, Streptomyces alanosinicus, Streptomyces ruber, Streptomyces gancidi-
cus, and Nocardiopsis aegyptia) for dye decolorization. Streptomyces globosus had
the maximum potential for the degradation of acid fast red dye under static (81.6 %)
and shaking (70.2 %) conditions. The authors suggested biosorption as dominant
mechanism for removal of dye from the solution. A 1.14-fold more biosorption was
observed with an increase in the size of the inoculum and a decrease in the con-
centration of starch. Studies conducted in 1990 s, also revealed that the Strepto-

myces species can be used for the degradation of azo dyes (Pasti et al. 1991 ;
Paszczynski et al. 1991 ; Burke and Crawford 1998 ).

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