Textile Dyes Degradation: A Microbial Approach for Biodegradation of Pollutants - Microbial Degradation of Synthetic Dyes in Wastewaters - page 188

(a) (b)

Fig. 1 Decolorization of Bromophenol blue (a) and Congo red (b) dyes by fungus Aspergillus
avus. Arrows indicating the zone of yellow color developed by the applied fungus during the dyes
decolorization/degradation (Singh and Singh 2010b )

azo and anthraquinonic dyes by fungi Aspergillus avus (Fig. 1 ) and Trichoderma

harzianum was also recorded (Singh and Singh 2010a , b ) which might be due to
both; primary, by the adsorption and absorption of these dyes by fungal mycelia
and secondary phenomenon, by producing extracellular enzymes during dye deg-
radation (Singh and Singh 2012 ). However, bacteria and others microorganisms
play an important role in the degradation of hazardous dyes, but among them, fungi
have key role in biodegradation process.

4 Bacteria Used in Dyes Degradation

Apart from fungi, bacteria and actinomycetes also have ability to degrade the dyes
and others pollutants. Various bacterial strains reduce azo dyes under both anaer-
obic and aerobic conditions to the corresponding amines (Meyer 1981 ). The bac-
teria Sphingomonas xenophaga BN6, Agrobacterium tumefaciens, Ralstonia
eutropha 335, Hydrogenophaga palleronii, Escherichia coli K12 and Flexibacter
liformis (Gram negative), Bacillus subtilis, Rhodococcus erythropolis and Lac-
tobacillus plantarum) (Gram negative) and Archea (Halobacterium salinarum) are
reported to reduce azo dyes under anaerobic condition.
Neelambari et al. ( 2013 ) found the decolorization of azo dyes by some bacterial
strains of Pseudomonas aeruginosa, Alcaligenes faecalis, Proteus mirabilis, Ser-
ratia marcescens and Bacillus licheniformis at static and shaking conditions. They
also found that applied bacterial strains decolorized the dyes ef ciently at about 3 %

salt concentration and completed decolorization of dye in 48 h of incubation. The
metabolites generated after the bacterial degradation were also found less toxic than
original dye as con

rmed by the phytotoxicity test. Jadhav et al. ( 2010 ) observed